A fertility tracker is meant to show you when your fertile days are while you are trying to conceive. There is a lot to choose from: sensors for the night, rings, thermometers with an app, hormone monitors with test sticks. In the first year they cost between about €46 and about €1,550 (according to the manufacturer's shop, as of October 2026).
We did not test the devices ourselves, and we do not name a winner. Instead, we have compiled what can be backed up with evidence: how each product measures, what it costs, what it is intended for as a medical device, which studies exist, and who paid for them.
The most important point first: For urine ovulation tests, a Cochrane review shows a probable increase in births. For temperature and mucus observation, a benefit is unclear, and fertility trackers and apps were not tested in randomized trials for this (Cochrane 2023). Most accuracy studies on individual fertility trackers were written or funded by the manufacturers themselves. What fits your situation is summarized in the decision guide.
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How we compared
We checked the same seven points for every product:
| Criterion | What we checked |
|---|---|
| Measuring principle | Hormones in urine or temperature, evaluated with or without an algorithm |
| What is measured | LH, estrogen (E3G), the progesterone breakdown product PdG, FSH, temperature, cervical mucus |
| Effort | When, how often, and for how long you measure or test |
| Cost in the first year | Purchase price plus subscription and consumables for 13 cycles |
| Medical device and intended purpose | What the product is intended for according to the instructions for use, conformity information, or the EU database EUDAMED |
| Independent evidence | Which studies exist, what served as the reference, and who funded them |
| Data privacy | Whether your cycle data goes into an app |
No grades, no ranking: The table below is sorted by measuring principle. The Inito device is missing because it is not officially available in Germany, Austria, and Switzerland.
To put the approval in context: Under EU law, products that support conception are medical devices (MDR Art. 2), and urine fertility tests for self-use are class B in vitro diagnostics (IVDR Annex VIII).
If a product is also intended for contraception, it falls into at least class IIb, with review by a notified body and clinical data (MDR Annex VIII, Rule 15). This higher class is not evidence of a benefit when trying to conceive.
For reliable contraception, the German-language S2k guideline currently does not recommend apps and fertility trackers that rely mainly on basal body temperature: Efficacy studies are said to be missing or to have considerable methodological weaknesses (AWMF 015-095).
Cycle trackers and ovulation tests: measuring principle and evidence
-
LH test strips
Urine test, read by eye
- Measures
- LH in urineonce a day from the start of testing, not with first morning urine
- Evidence
- Cochrane 2023: Urine ovulation tests probably lead to more births than no ovulation prediction (1 study, moderate-certainty evidence). The only study on this came from the manufacturer SPD and used a Clearblue test for LH and estrogen; none used simple strips
-
Clearblue Advanced Digital Ovulation Test
Digital urine test
- Measures
- LH and estrogen (E3G) in urinefirst urine of the day, daily from the start day given in the table
- Evidence
- Manufacturer-funded study with a similar test connected to an app (844 women): after 1 cycle, 25.4% pregnant versus 14.7% without a test
-
Clearblue Advanced Fertility Monitor
Hormone monitor with test sticks
- Measures
- LH and estrogen in urinefirst urine of the day on the requested days, usually 10 per cycle
- Evidence
- Study with the previous model (653 women): after 2 cycles, 22.7% pregnant versus 14.4% without a monitor
-
Mira Ultra4
Hormone monitor with test sticks
- Measures
- LH, E3G, PdG, and FSH in urine, as numerical valuesin the morning, test schedule from the app, usually 18 to 22 sticks per cycle
- Evidence
- 2026 study with ultrasound as the reference: the LH peak matched ovulation within ±1 day in 96%
-
trackle
Vaginal temperature sensor with app
- Measures
- Core body temperature, cervical mucus entered manuallyat night during sleep, at least 4 hours
- Evidence
- Only a small analysis funded by the manufacturer (25 users); the symptothermal method itself is well studied
-
Tempdrop
Temperature armband with app
- Measures
- Skin temperature on the upper armat night during sleep, wear for at least 3 hours
- Evidence
- Study with the manufacturer’s involvement (125 women): ovulation day within ±2 days of the LH test in 93% of cycles
-
Oura Ring 5
Smart ring with app
- Measures
- Skin temperature on the finger, heart rateautomatically at night
- Evidence
- Manufacturer’s study with 964 users: 96% of ovulations detected, with an average deviation of 1.3 days
-
Natural Cycles
App with thermometer or wearable
- Measures
- Basal or skin temperature, period data, optional LH teststhermometer in the morning or wearable at night, at least 5 measurements per week
- Evidence
- Manufacturer-funded observational study without a control group: 61% pregnant after 6 cycles, 74% after 12 cycles
-
Daysy
Fertility tracker with thermometer
- Measures
- Basal body temperature under the tongue, period entered manuallyin the morning after waking up, about 60 seconds
- Evidence
- No independent study on use when trying to conceive; a manufacturer-funded contraception study was retracted in 2019
-
cyclotest mySense Lifetime
Bluetooth basal body thermometer with app
- Measures
- Basal body temperature, optional cervical mucus and LH testsin the morning after waking up, 30 to 60 seconds
- Evidence
- No study on the current device; studies on the previous device and on the symptothermal method
-
Ovy
App with Bluetooth basal body thermometer
- Measures
- Basal body temperature, cervical mucus, optional LH testsin the morning after waking up
- Evidence
- No study on the device; method is symptothermal
Sorted by measuring principle, not a ranking.
Hormones or temperature: what the measuring principles can do
The devices in this comparison work on three principles. The most important difference: Do they announce ovulation beforehand, or do they confirm it only afterward?
| Principle | Examples | What it shows | Main limitation |
|---|---|---|---|
| LH in urine | LH test strips | the LH surge, after which ovulation can follow at some point within 2 days (ASRM 2022) | a positive test does not prove ovulation |
| LH and estrogen, in some cases PdG in urine | Clearblue tests and monitor, Mira | additionally days before the LH surge, with PdG also a confirmation afterward | more expensive than simple LH strips, pregnancy data at most for earlier models or variants |
| Temperature | trackle, Tempdrop, Oura, Natural Cycles, Daysy, cyclotest, Ovy | the rise after ovulation, the algorithm projects forecasts from previous cycles | confirms ovulation only in hindsight |
Temperature shows ovulation only afterward
After ovulation, progesterone raises basal body temperature by a few tenths of a degree, by about 0.4 to 0.9°F (0.2 to 0.5°C) depending on the source (WHO 2022, frauenaerzte-im-netz.de 2018). On average, the rise comes 2.4 days after the LH surge (Prior 1990, cited in Henry 2024). In an analysis of Natural Cycles, the ovulation estimated from temperature came on average 1.9 days after the first positive LH test; the study comes from the manufacturer (Berglund Scherwitzl 2015).
For trying to conceive, that is the crucial point. The fertile window comprises the 5 days before ovulation and the day of ovulation (familienplanung.de 2026), and the chance is highest with intercourse on the day before ovulation (ASRM 2022). In a study cited by the FSRH, the chance of conception more than 2 days after the day of the temperature rise was negligible (FSRH 2015). So when the chart rises, the window in the current cycle is largely over.
Even experts rarely read the day of ovulation precisely from the chart: Experienced physicians, working by consensus, estimated the day of the LH peak from the chart to within ±1 day in only 22.1% of cycles (Bauman 1981). The British NICE guideline advises against using temperature charts to confirm ovulation (NICE 2026). Illness, a short or disturbed night, alcohol, or late eating can raise the morning temperature (IQWiG 2025). With widely varying sleep times, the values jump, which is why shift work was an exclusion criterion in one study (Henry 2024).
Wristbands and rings measure skin temperature at night. According to the S2k guideline, this is not the same as basal body temperature, and such systems are considered experimental there with regard to contraception (AWMF 015-095). A meta-analysis found an accuracy of 0.90 for wearables for the day of ovulation to within ±2 days, and 0.61 to within ±1 day. For the exact day, the estimate was practically uninformative, the devices did worse with irregular cycles, and the quality of the evidence was very low (Shi 2026). How to measure and evaluate basal body temperature yourself is explained in the guide How to measure basal body temperature.
Calendar apps only work with averages
Apps and web calculators that work only with cycle length and period data are often off. Of 20 websites and 33 apps, only 1 website and 3 apps correctly predicted the fertile window for a 28-day cycle (Setton 2016). In 949 women, apps matched the day of ovulation determined by an LH test in at most 21% of cases (Johnson 2018, two authors work for the manufacturer of the Clearblue tests).
One reason: The 28-day cycle is rarer than you might think. In the same study, 34% of women believed they had one, but in fact 15% did. In more than 600,000 app cycles, only 13% lasted exactly 28 days, and even then ovulation came on average after day 14 (Bull 2019, funded by the app provider). The fertile window lay entirely between cycle days 10 and 17 in only about 30% of women (Wilcox 2000).
Data box: what “96% of ovulations detected” means
Figures like these describe how close a device's estimate came to the reference day in a study. They say nothing about your chance of getting pregnant. Three questions help put them in context: What was the reference, ultrasound or an LH test? Was ovulation predicted, or only determined after the cycle ended? And who paid for the study? In most of the wearable studies in this comparison, the reference was an LH test, and employees or founders of the manufacturer were involved.
What studies show about getting pregnant
How precisely a device pinpoints ovulation is one question. Whether more babies are born with it is another. For that there is a Cochrane review of 7 randomized trials with 2,464 women or couples (Cochrane 2023):
| Approach | Result | Evidence |
|---|---|---|
| Intercourse timed by a urine ovulation test | Live births probably more frequent (RR 1.36): 16% without a test, 16 to 28% with a test | moderate, 1 study with 844 women |
| Intercourse timed by a urine ovulation test | Pregnancies probably more frequent (RR 1.28): 20 to 28% instead of 18% | moderate, 4 studies with 2,202 women |
| Cycle observation after training, without a urine test (symptothermal method, cervical mucus method) | unclear whether the live birth rate changes (RR 0.95) | low, 2 studies with 157 women |
Fertility trackers, wearables, and cycle apps were not tested in any of these randomized trials.
There are caveats. The authors limit the benefit to women under 40 who have been trying to get pregnant for less than 12 months. The urine studies did not test a simple LH test strip but a commercial system that measures LH and estrogen. The rating was downgraded, among other reasons, because of commercial funding. The only study on live birth is a follow-up analysis of a randomized trial by the manufacturer of Clearblue with 844 women who had been trying for at most 6 months. The manufacturer funded the analysis, and all authors were employed by it (Johnson 2022). Whether timed intercourse changes stress levels is unclear.
On the symptothermal method, that is, temperature plus cervical mucus, there is one observational study on trying to conceive: After training, 38% of 187 women with reduced fertility were pregnant after 8 months, an estimated 21.6% without training. There was no control group, and the study concerns the method, not a particular device (Frank-Herrmann 2017).
At least as important as any device is how often you have intercourse. According to the ASRM, the chance per cycle was similar with intercourse daily, every other day, and every 3 days in the fertile window, and lowest with intercourse only once. Cycle tracking is meant to guide intercourse, not replace regular sex, because sex strictly by schedule can increase stress and lower sexual satisfaction (ASRM 2022). NICE names intercourse every 2 to 3 days as optimal (NICE 2026).
To put manufacturer figures in perspective: More than 80% of couples get pregnant within a year if the woman is under 40 and they have regular intercourse without contraception. Of the rest, about half get pregnant in the second year (NICE 2026).
Urine tests and hormone monitors
LH test strips: the simple option
Simple test strips or test sticks use lines to show whether LH in the urine has risen. If the test line is as strong as or darker than the control line, the test counts as positive. According to the package insert of a drugstore house brand, ovulation is then likely within the next 24 to 36 hours. You test once a day starting on a start day that depends on your cycle length, and for this brand explicitly not with first-morning urine.
Cost: €5.95 for 10 tests (drugstore house brand, according to the manufacturer's shop, as of October 2026). With 6 tests per cycle, that comes to about €46 in the first year. According to the package insert, about 90% of women with ovulation and a regular cycle see the surge within 8 to 10 test days. If you plan on 10 tests per cycle, it is about €77.
Evidence: well studied, with ultrasound as the reference. In 101 women with infertility, the urinary LH surge matched ovulation on ultrasound in 98 cases, the temperature chart only in 74% (Guermandi 2001). The ESHRE summarizes the agreement of urinary LH measurements with ultrasound in the studies as 98 to 100% (ESHRE 2023).
Limitations: In about 7% of cycles, the result is false positive (ASRM 2022). A positive test does not prove ovulation: In LUF syndrome, LH rises normally without an egg being released, described in 10.7% of cycles of normally fertile women (Su 2017). In PCOS, ovulation tests can be misleading according to manufacturers. The claim of more than 99.9% accuracy on the package insert is based on a comparison with another LH test, not with actual ovulation.
Medical device: in vitro diagnostic for self-use, not for contraception. Data privacy: no app needed.
How to start, read, and interpret the tests is explained in the guide Ovulation test.
Clearblue digital ovulation test: LH and estrogen
The Clearblue Advanced Digital Ovulation Test measures LH and estrogen (E3G) in the first urine of the day. When estrogen rises, the display shows a flashing smiley for high fertility, and at the LH surge a solid smiley for 48 hours. In this way, the test also marks days before the LH surge. You test daily starting on a start day according to a chart, on cycle day 8 for a 28-day cycle.
Cost: Kit with 30 tests €49.99 (MSRP according to the manufacturer, as of October 2026). Assuming 8 tests per cycle, that comes to about €173 in the first year. The manufacturer does not state a typical number of tests.
Evidence: In a randomized trial with 844 women using a similar, app-connected test system for LH and estrogen, 25.4% were pregnant after one cycle, versus 14.7% without a test. After two cycles it was 36.2% versus 28.6% (Johnson 2020). The manufacturer funded the study, and four authors were employed by it. This exact product was not tested.
Limitations: According to the manufacturer, the test does not show peak fertility in about 8% of cycles. Misleading results are possible with PCOS, during menopause, with medications that contain LH or hCG, and with tetracyclines, among other things.
Medical device: in vitro diagnostic, only for trying to conceive, not for contraception. Data privacy: result on the display, the manufacturer's cycle app is optional.
Clearblue Fertility Monitor: reader with test sticks
The monitor reads urine test sticks and measures LH and estrogen. It requests tests on specific cycle days, usually 10 per cycle, up to 20 for long or irregular cycles, each with the first urine of the day in a personally set 6-hour window. It stores the data of the last 6 cycles in the device.
Cost: Monitor €139.99, 30 test sticks €81.50 (MSRP according to the manufacturer, as of October 2026). With 10 tests, that is €27.17 per cycle and about €493 in the first year.
Evidence: In a randomized trial with 653 evaluable women, 22.7% with the monitor were pregnant after two cycles, versus 14.4% without the monitor (Robinson 2007). The data were self-reported in a diary, and the older predecessor model was tested. According to the Cochrane review, the study was funded by Unipath, then the manufacturer of Clearblue. The advertising claim of 89% higher chances corresponds to the adjusted odds ratio of this study (odds ratio 1.89), and in absolute terms it is the 22.7% versus 14.4% mentioned. In an ultrasound study with 53 women, ovulation fell within the two days of peak fertility shown by the predecessor monitor in 91.1% of cycles, and never before them (Behre 2000, funding not stated).
Limitations: suitable for cycle lengths of 21 to 42 days. If cycles are always shorter than 23 or longer than 37 days, it may not detect the LH surge. According to the manufacturer, misleading results are possible with PCOS, during menopause, and with impaired liver or kidney function.
Medical device: in vitro diagnostic, exclusively for trying to conceive. Data privacy: data stay in the device.
Mira: hormone values as numbers
Mira uses an analyzer and test sticks to measure LH, estrogen (E3G), PdG, and with the Ultra4 sticks also FSH, and shows the values as numbers in the app. The PdG rise is meant to confirm ovulation. The app gives a testing schedule, and according to the manufacturer most people need 18 to 22 sticks per cycle.
Cost: Ultra4 kit with 20 sticks €266.95, then 20 sticks for €106.95 per cycle (according to the manufacturer's shop, as of October 2026, shop in English). That comes to about €1,550 in the first year, the highest figure in this comparison.
Evidence: In a prospective, blinded study of 52 women with cycle lengths of 24 to 38 days and 890 ultrasound examinations, ovulation fell within ±1 day of the LH peak measured by Mira in 96% of the evaluated cycles (Bouchard 2026). The manufacturer also names PCOS and irregular cycles as areas of use, and this study says nothing about that. Funding and conflicts of interest are not stated in the abstract. In other papers, the first author states that his doctoral work is supported by a scholarship that the Mira manufacturer co-funds. A very small study with 4 women and no involvement of the Mira manufacturer (two authors are partners in a biomarker company) found values that fluctuated more than in blood and no sign from E3G of the start of the fertile window, but Mira correctly detected the transition into the second half of the cycle (Usala 2024). We did not find studies on pregnancy rates.
Medical device: The official shop does not state a CE marking or risk class specifically. “FDA registered” means a registration, not an approval. Data privacy: The values appear in the app.
If you see your hormones as numbers: What an LH value does and does not tell you is explained in the guide LH levels.
Temperature sensors for the night
trackle: vaginal temperature sensor
trackle is a sensor you wear overnight in the vagina like a tampon. It measures core body temperature every minute. A sleep or rest period of at least 4 hours is required, and the time of day does not matter. In the morning, the sensor goes into the box, which transmits the data to the app via Bluetooth. You enter cervical mucus yourself every day, and the evaluation follows the symptothermal method. For trying to conceive, the app shows an ovulation forecast in the calendar from the first evaluated cycle.
Cost: €269.90 to buy, the app is free, and according to the manufacturer the sensor lasts 30 months. Alternatively there is a subscription at a regular €13.49 per month, as a promotion in October 2026 for €10.79. It has a 24-month minimum term and cannot be paused during pregnancy (according to the manufacturer's shop, as of October 2026).
Evidence: We did not find a peer-reviewed study specifically on trackle. The German Clinical Trials Register (Deutsches Register Klinischer Studien) lists a retrospective evaluation funded by trackle, with 25 users over 12 cycles each. According to the register, the algorithm reached the same results as manual evaluation following the rules of the method, and no publication is listed (DRKS00031801). The Pearl Index values on the website come from studies on the symptothermal method in general and concern contraception (Frank-Herrmann 2007).
Limitations: According to the manufacturer, only suitable if ovulation takes place. Temperature confirms it only in hindsight.
Medical device: class IIb according to the manufacturer, because the intended purpose also includes contraception, and still certified under the old Medical Devices Directive. The instructions for use name trying to conceive and contraception as the purpose. Data privacy: evaluation via the app.
Tempdrop: temperature armband on the upper arm
Tempdrop is a sensor in a band worn on the upper arm. During sleep it continuously measures skin temperature over the axillary artery, and an algorithm filters out disturbances and calculates one value per night. At least 3 hours of wear time with at least 2 hours of sleep are required, and according to the manufacturer also during the day for shift work. You can optionally enter cervical mucus.
Cost: Sensor €229 (according to the manufacturer's shop, shop in English), the premium app needed for the ovulation evaluation €49 per year (according to the German App Store), 2 months are included with the purchase, as of October 2026. That comes to about €278 in the first year. Without premium there is only a temperature chart, calendar, and symptom entry.
Evidence: In 194 cycles from 125 women, the ovulation day estimated by the sensor fell within ±2 days of the reference day from an LH test in 181 cycles (93.3%), no ultrasound (Shpaichler 2025). The values of 96.8% sensitivity and 99.1% specificity also given in the study do not concern ovulation detection but whether individual cycle days were correctly classified as fertile or infertile. What was tested was an algorithm that calculates only after the cycle ends, so not a prediction. The founder and an employee of Tempdrop are co-authors. Data on pregnancy rates are missing.
Medical device: class I according to EUDAMED. Intended purpose according to the provider: observing fertility and planning pregnancy, explicitly not for contraception. Data privacy: evaluation via the app.
Oura Ring: skin temperature at the finger
The ring measures skin temperature at the finger at night, as well as heart rate, heart rate variability, and respiratory rate. In the EU, the “Fertile Window” feature is a CE-marked medical device, only as a conception aid and not for contraception, and the ring itself is not a medical device. According to the manufacturer, there is little data for cycles shorter than 21 or longer than 35 days and for diagnosed infertility. It can be linked with Natural Cycles, with its own subscription.
Cost: Oura Ring 5 from €429, plus the membership needed for the cycle features at €69.99 per year (according to the manufacturer's shop, as of October 2026). That comes to about €499 in the first year.
Evidence: In 1,155 cycles with ovulation from 964 users, the algorithm detected 96.4% of ovulations and was off by an average of 1.26 days, compared with 3.44 days for the calendar method. It was accurate to ±1 day in 68% and to ±2 days in 87.9% of cycles (Thigpen 2025). What was tested was whether the algorithm detects ovulation in hindsight, not the prediction of the fertile window in the current cycle. All authors work at Oura. The reference was self-entered LH tests, not ultrasound. Only cycles with ovulation were evaluated, and how often the ring shows ovulation in cycles without one is still an open question. For cycle disorders, such as PCOS, the authors say the estimates should be interpreted only with caution.
Data privacy: evaluation via the app and membership.
Cycle apps and fertility trackers
Natural Cycles: app with thermometer or wearable
Natural Cycles is an app classified as a medical device. You measure either in the morning with a thermometer or at night with the NC° Band or a compatible wearable such as the Oura Ring or Apple Watch, and at least 5 measurements per week are recommended. The algorithm detects the temperature rise after ovulation and combines it with your period data, and you can optionally enter LH tests. For trying to conceive there is the Plan Pregnancy mode, and all modes are included in the subscription.
Natural Cycles cost: The annual subscription costs €119.99, and a thermometer or the band is included (according to the German App Store, as of October 2026). Different prices apply in Austria and Switzerland. With an Oura Ring, its membership comes on top.
Evidence: In an observational study without a control group of 5,376 women in Plan Pregnancy mode, the probability of pregnancy was 61% after 6 cycles and 74% after 12 cycles, with a median of 4 cycles. Self-reported positive tests were counted (Favaro 2021). Natural Cycles funded the study, and several authors are employees or founders. Of the women, 30.5% dropped out early, and some of them switched back to contraception mode, which limits the figures. In an assessment of fertility apps without manufacturer involvement, the then-current version of Natural Cycles received 2 of 30 points, and the best symptothermal apps 20 of 30 (Freis 2018).
Limitations: The system does not measure hormones. Natural Cycles itself describes its algorithm as retrospective, and temperature confirms ovulation only afterward (Bull 2019).
Medical device: In the US, the FDA classified Natural Cycles in 2018 as software for contraception or pregnancy planning for women aged 18 and older, class II (FDA 2018). In the EU, according to the manufacturer, the app is certified as a class IIb medical device for contraception. Data privacy: evaluation via the app.
Daysy: fertility tracker with a traffic-light display
Daysy is a handheld device with a built-in temperature sensor. You measure in the morning after waking up, under the tongue, for about 60 seconds, before getting up and after at least one hour of sleep, and according to the manufacturer a fixed time of day is not necessary. You also enter your period. An algorithm evaluates the data and shows traffic-light colors: red for fertile, green for not fertile, yellow in the learning phase, flashing red for the expected ovulation.
Cost: List price €299, on sale in October 2026 for €249 (according to the manufacturer's shop, as of October 2026). No subscription, and the app is free.
Evidence: We did not find a study on trying to conceive or on time to pregnancy. A manufacturer-funded study on contraception from 2018 (125 women, retrospective survey) was retracted by the journal's editors-in-chief in 2019. An independent expert review had confirmed fundamental methodological flaws, and the authors objected to the retraction (Reproductive Health 2019). The advertised 99.4% describes, according to the manufacturer's fact sheet, that only 0.6% of the days shown as green (not fertile) fell within a fertile window extended to 8 days. The basis is a retrospective evaluation of user data with manufacturer involvement (van de Roemer 2021). The abstract does not mention a comparison with hormone or ultrasound measurements. The figure says nothing about the chance of getting pregnant.
Limitations: Daysy evaluates only temperature and period, without cervical mucus. In the first 2 to 4 cycles, the algorithm is still learning (yellow days), and temperature confirms ovulation only in hindsight.
Medical device: class I according to EUDAMED. Intended purpose according to the instructions for use: promoting conception, explicitly not a contraceptive. Data privacy: The device itself shows the result.
cyclotest mySense: basal thermometer with app
cyclotest mySense is a Bluetooth basal thermometer with an app. You measure in the morning after waking up and before getting up, for about 30 to 60 seconds, orally, vaginally, or rectally. The app evaluates the temperature rise, optionally also cervical mucus or LH tests, and shows fertile, highly fertile, and infertile days. There is no switchable trying-to-conceive mode, but the manufacturer explicitly promotes it for this use.
Cost: Lifetime variant €139.90 with premium app without a subscription, alternatively Flex for €49.90 (both according to the manufacturer's shop) plus €39.99 per year for premium (according to the German App Store), as of October 2026.
Evidence: We did not find a study on the current device and today's app. Older studies concern the predecessor device and contraception (Freundl 1998).
Limitations: At least 5 hours of sleep before measuring are required, and with Flex there is only a basic version without a subscription. Temperature confirms ovulation only in hindsight.
Medical device: thermometer class IIa with review by a notified body, app class I without a notified body. Intended purpose: fertility observation and family planning, no explicit contraception purpose. Data privacy: evaluation via the app.
Ovy: app with basal thermometer
Ovy is an app with a Bluetooth basal thermometer for measuring in the mouth or vagina. It evaluates temperature and cervical mucus using the symptothermal method, in trying-to-conceive mode optionally also ovulation tests by photo or entry, and shows the day of ovulation and the six most fertile days. According to the instructions for use, it is not suitable for cycle lengths under 16 or over 56 days and for known infertility in the woman or man.
Cost: Thermometer €79, Premium €83.92 per year, alternatively a trying-to-conceive bundle with lifetime Premium for €149 (according to the manufacturer's shop, as of October 2026).
Evidence: We did not find a study on the device. The Pearl Index on the shop page refers to the symptothermal method in general. In the same assessment of fertility apps, the Ovy version at the time received 3 of 30 points (Freis 2018). At that time it worked without data from the current cycle, and the assessment dates from before today's certification. We did not find a new assessment without manufacturer involvement.
Medical device: app class IIb under the MDR, certified by a notified body, intended purpose contraception or pregnancy planning. Data privacy: evaluation via the app.
What a fertility tracker costs in the first year
This section applies to Germany only.
The purchase price says little, and subscriptions and consumables are what matter. The figures are calculated for 13 cycles and sorted by cost, not by quality (according to the manufacturer's shop, App Store, or MSRP, as of October 2026). The links to the manufacturers are in the comparison table above.
| Product | Year 1, approx. | Ongoing costs |
|---|---|---|
| LH test strips (drugstore house brand) | €46 to €77 | €3.57 per cycle with 6 tests, €5.95 with 10 tests |
| Natural Cycles | €120 | Annual subscription €119.99, thermometer or band included |
| cyclotest mySense Lifetime | €140 | nothing |
| Ovy | €163 | Premium €83.92 per year, alternatively trying-to-conceive bundle with lifetime Premium for €149 one-time |
| Clearblue digital ovulation test | €173 | €1.67 per test, 8 tests per cycle assumed |
| trackle | €270 | nothing, service life according to the manufacturer 30 months |
| Tempdrop | €278 | Premium app €49 per year |
| Daysy | €299 | nothing, on sale in October 2026 for €249 |
| Clearblue Fertility Monitor | €493 | €27.17 per cycle with 10 test sticks |
| Oura Ring 5 | €499 | Membership €69.99 per year |
| Mira Ultra4 | €1,550 | €106.95 per cycle for 20 sticks |
If you combine a temperature device with ovulation tests, you pay for both. For devices with no ongoing costs, the price is spread over several years, for trackle according to the manufacturer over 30 months.
For many, an ovulation test plus an Ovulation Calculator is enough
If your cycle is regular and you have only been trying for a few months, you usually do not need an expensive device. With a regular monthly cycle, ovulation probably takes place (NICE 2026). A simple approach:
- Use the Ovulation Calculator to roughly estimate your fertile days and find the start day for the tests. It calculates by calendar and does not confirm ovulation.
- From the start day, do an LH test once a day until it is positive.
- Have sex regularly in the fertile window: Every 1 to 2 days gives the highest rates according to the ASRM, and 2 to 3 times per week is nearly equivalent (ASRM 2022).
Why that is enough: LH tests reliably detect the surge before ovulation (Guermandi 2001), urine ovulation tests are the only method with a probable benefit in the Cochrane review, and with frequent intercourse, an ovulation day pinpointed to the exact day matters less (ASRM 2022). However, simple strips themselves were not tested in the Cochrane studies. Basal body temperature alone is not well suited to getting pregnant according to the ACOG, because it only shows that ovulation has already happened (ACOG 2025).
What works for whom?
The overview classifies typical situations. It is not a purchase recommendation for a particular product and does not replace a conversation with a doctor.
| Your situation | What the data says | What you can look out for |
|---|---|---|
| Regular cycle, you have only just started trying | Ovulation probable (NICE 2026), probable benefit shown only for urine ovulation tests (Cochrane 2023) | LH test plus Ovulation Calculator, plus intercourse every 2 to 3 days |
| Irregular cycle or PCOS | Calendar apps are often off, LH tests and hormone monitors can be misleading in PCOS according to manufacturers, wearables do worse with irregular cycles (Shi 2026) | First have a doctor clarify whether and when ovulation takes place |
| Shift work or changing sleep times | Morning temperatures jump with irregular sleep (Henry 2024) | Simple LH strips are tested during the day. For temperature devices, check the instructions for use to see whether they also measure after daytime sleep, according to the manufacturer for example trackle (at least 4 hours of rest) and Tempdrop. We did not find studies specifically on shift work |
| Small budget | Urine ovulation tests have the best evidence (Cochrane 2023) | LH test strips cost about €46 to €77 in the first year depending on the number of tests, the Ovulation Calculator nothing |
| You want to know whether ovulation happens at all | Temperature charts are not suited to confirming it according to NICE, and doctors measure progesterone in the blood (NICE 2026) | Ask a gynecologist instead of buying a more expensive device |
| You already wear a ring or smartwatch | Studies mostly come from manufacturers, and the evidence for wearables is very low (Shi 2026) | Include subscription costs, treat results as an estimate |
| No pregnancy after 12 months, after 6 months from age 35, over 40, or a known cause | Medical evaluation recommended (AWMF 015-085, 2026; NICE 2026) | No device replaces the evaluation |
Data privacy: cycle data is health data
Period, temperature, hormone values, and information about sex are health data or data concerning sex life under the GDPR. Processing them is prohibited in principle, except, for example, with your explicit consent for specified purposes (GDPR Art. 9).
In practice, things often look different. An analysis of the 23 most popular women's health apps found that 20 shared user data with third parties, only 16 showed a privacy policy, only 12 obtained consent, and 3 collected data even before consent (Alfawzan 2022). In the US, the consumer protection agency FTC (Federal Trade Commission) reached a settlement in 2021 with the provider of a widely used period and ovulation app. The allegation: Health data had been passed on to analytics and marketing services despite promises to the contrary (FTC 2021).
We did not examine the data practices of the individual products in this comparison. Before buying, it helps to look at the privacy policy: Where is the data stored, does it go to third parties, can you delete it? If you want to share as little data as possible: Simple LH strips need no app, with the Clearblue Advanced Digital Ovulation Test the app is optional, the Clearblue monitor stores data in the device, and Daysy shows the result on the device itself.
When a medical evaluation matters more than any device
No device in this comparison measures anything in your partner, in the fallopian tubes, or in the ovarian reserve. The German-language guideline names clear time frames (AWMF 015-085, 2026):
- Under 35: evaluation after 12 months without pregnancy.
- From 35: after 6 months.
- Over 40: immediately at a reproductive medicine center.
The British NICE guideline goes even further: From age 36 and with a known or suspected cause, a referral for specialist fertility advice should be offered as early as the first doctor's appointment (NICE 2026).
Further pointers come from the German PMOS guideline and from manufacturers:
- Irregular cycle: Repeated cycles shorter than 21 or longer than 35 days, or fewer than 8 cycles per year, point to infrequent or absent egg maturation, according to the German PMOS guideline (AWMF 089-004, 2026). More in the guide Getting pregnant with PCOS.
- No LH surge: If the ovulation test shows no surge for 3 cycles in a row, one manufacturer recommends a medical evaluation.
- Unusual chart: Cycle charting can give indications of a short high-temperature phase of under 10 days or of absent ovulation. An indication is not a diagnosis, though (AWMF 015-095).
According to NICE, whether ovulation takes place is checked by the doctor through progesterone in the blood in the middle of the second half of the cycle, even with a regular cycle (NICE 2026). The ESHRE, by contrast, does not consider confirmation routinely necessary with a regular cycle (ESHRE 2023). What an evaluation includes and what it costs is explained in the guide Fertility test for women.
Frequently asked questions
What is the best fertility tracker for trying to conceive?
There is no winner here, and we did not test the devices ourselves. For getting pregnant, a probable benefit is shown only for urine ovulation tests. For temperature and mucus observation it is unclear, and fertility trackers and apps were not tested in randomized trials for this (Cochrane 2023). Which device fits depends on your cycle, your sleep, your budget, and how much effort you want to put in.
Is an ovulation test enough instead of a fertility tracker?
For many people, yes, especially with a regular cycle in the first months. LH tests reliably detect the surge before ovulation, and in 101 women they matched ultrasound in 98 cases (Guermandi 2001). With frequent intercourse in the fertile window, an ovulation day pinpointed to the exact day is less important (ASRM 2022).
How meaningful are trackle reviews?
Reviews online are anecdotal. We did not find a peer-reviewed study on trackle, only an unpublished evaluation funded by trackle with 25 users (DRKS00031801). The symptothermal method behind it is well studied, especially for contraception (Frank-Herrmann 2007).
What do Daysy reviews and studies say about trying to conceive?
We did not find a study on trying to conceive. A manufacturer-funded study on contraception was retracted in 2019 (Reproductive Health 2019). Advertising claims about pregnancies in the first cycle come, according to our research, from a user survey by the manufacturer, not from a peer-reviewed study.
How much does Natural Cycles cost?
The annual subscription costs €119.99, and a thermometer or the NC° Band is included (according to the German App Store, as of October 2026). Different prices apply in Austria and Switzerland. Anyone who uses an Oura Ring pays the Oura membership of €69.99 per year in addition.
What do Natural Cycles reviews and studies say about getting pregnant?
Reviews from individual users are anecdotal. In the observational study funded by the manufacturer, 61% of women were pregnant after 6 cycles and 74% after 12 cycles, with a median of 4 cycles, and 30.5% dropped out early (Favaro 2021). Without a control group, there is no way to tell how much of this is due to the app. In a German study of 346 women who used natural family planning to get pregnant, the figures were 81% after 6 cycles and 92% after 12 cycles (Gnoth 2003). The groups are not directly comparable.
Is the Clearblue Fertility Monitor reliable?
It measures LH and estrogen in urine. In an ultrasound study with the predecessor monitor, ovulation fell within the two displayed days of peak fertility in 91.1% of cycles, never before them (Behre 2000). For the predecessor model there is also a randomized trial: After 2 cycles, 22.7% with the monitor and 14.4% without were pregnant, the data were self-reported, and the manufacturer at the time funded it (Robinson 2007). In the first year it costs about €493 (MSRP according to the manufacturer, as of October 2026). With PCOS, according to the manufacturer, it can give misleading results.
Do fertility trackers work with PCOS or an irregular cycle?
Only to a limited extent. LH tests and hormone monitors can be misleading in PCOS according to manufacturers, wearables pinpointed ovulation less accurately with irregular cycles (Shi 2026), and some systems are, according to the manufacturer, only suitable if ovulation takes place. Repeated cycles shorter than 21 or longer than 35 days point, according to the German guideline, to infrequent or absent egg maturation (AWMF 089-004, 2026). In that case, a medical evaluation is a more sensible first step than a device.
Sources
Guidelines and position statements
- Gibbons T et al.: Timed intercourse for couples trying to conceive, Cochrane Database Syst Rev 2023, CD011345.pub3
- NICE NG257: Fertility problems, Initial advice to people concerned about delays in conception, NICE, March 31, 2026
- NICE NG257: Defining infertility and initial assessment, NICE, March 31, 2026
- NICE NG257: Investigation of fertility problems and management strategies, NICE, March 31, 2026
- ESHRE Guideline Group on Unexplained Infertility: Evidence-based guideline: unexplained infertility, Hum Reprod 2023, ESHRE
- ESHRE Evidence-based Guideline: Unexplained Infertility, full text with evidence synthesis, ESHRE, 2023
- Practice Committee of ASRM and SREI: Optimizing natural fertility: a committee opinion, Fertil Steril 2022;117:53-63, ASRM
- Fertility Awareness-Based Methods of Family Planning (FAQ024), ACOG, last reviewed February 2025
- FSRH Clinical Guidance: Fertility Awareness Methods, Faculty of Sexual & Reproductive Healthcare, 2015
- S2k guideline Non-hormonal contraception, AWMF 015-095, DGGG, OEGGG, and SGGG, as of December 2023
- Diagnostics and therapy before medically assisted reproduction treatment, S2k guideline AWMF 015-085, version 2.0, DGGG, OEGGG, and SGGG, as of April 2026
- Patient guideline polyendocrine metabolic ovarian syndrome (PMOS, formerly PCOS), AWMF 089-004, as of June 2026
- Family Planning: A Global Handbook for Providers, chapter Fertility Awareness Methods, WHO and Johns Hopkins CCP, 2022
Consumer information
- Getting pregnant: ovulation and the fertile days, familienplanung.de, Federal Institute for Public Health, January 7, 2026
- Determining your fertile days yourself: methods, frauenaerzte-im-netz.de (BVF and DGGG), July 9, 2018
- Contraception with natural family planning methods, gesundheitsinformation.de, IQWiG, February 19, 2025
Law and regulators
- Regulation (EU) 2017/745 on medical devices (MDR), European Parliament and Council, 2017
- Regulation (EU) 2017/746 on in vitro diagnostic medical devices (IVDR), European Parliament and Council, 2017
- Regulation (EU) 2016/679 (GDPR), Article 9, European Parliament and Council, 2016
- De Novo Classification Request for Natural Cycles (DEN170052), Decision Summary, U.S. Food and Drug Administration, 2018
- Developer of Popular Women's Fertility-Tracking App Settles FTC Allegations that It Misled Consumers About the Disclosure of their Health Data, U.S. Federal Trade Commission, 2021
- DRKS00031801: A comparison of symptothermal cycle observation using an intravaginal temperature sensor with conventional temperature recording, German Clinical Trials Register, 2023
Studies on cycles, apps, and temperature
- Setton R, Tierney C, Tsai T: The Accuracy of Web Sites and Cellular Phone Applications in Predicting the Fertile Window, Obstet Gynecol 2016
- Johnson S, Marriott L, Zinaman M: Can apps and calendar methods predict ovulation with accuracy?, Curr Med Res Opin 2018
- Wilcox AJ, Dunson D, Baird DD: The timing of the fertile window in the menstrual cycle, BMJ 2000
- Bull JR et al.: Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles, npj Digital Medicine 2019, funded by the app provider
- Berglund Scherwitzl E, Lindén Hirschberg A, Scherwitzl R: Identification and prediction of the fertile window using NaturalCycles, Eur J Contracept Reprod Health Care 2015
- Henry S et al.: Prospective 1-year assessment of within-woman variability of follicular and luteal phase lengths, Hum Reprod 2024;39(11):2565-2574
- Bauman JE: Basal body temperature: unreliable method of ovulation detection, Fertil Steril 1981;36(6):729-733
- Shi Y et al.: The diagnostic accuracy of wearable digital technology in detecting fertility window and menstrual cycles, npj Digital Medicine 2026;9:139
- Gnoth C et al.: Time to pregnancy: results of the German prospective study and impact on the management of infertility, Hum Reprod 2003
- Frank-Herrmann P et al.: The effectiveness of a fertility awareness based method to avoid pregnancy in relation to a couple's sexual behaviour during the fertile time, Hum Reprod 2007
- Frank-Herrmann P et al.: Natural conception rates in subfertile couples following fertility awareness training, Arch Gynecol Obstet 2017
- Alfawzan N, Christen M, Spitale G, Biller-Andorno N: Privacy, Data Sharing, and Data Security Policies of Women's mHealth Apps, JMIR mHealth and uHealth 2022
Studies on ovulation tests and hormone monitors
- Guermandi E et al.: Reliability of ovulation tests in infertile women, Obstet Gynecol 2001;97(1):92-96
- Su HW et al.: Detection of ovulation, a review of currently available methods, Bioeng Transl Med 2017
- Johnson S, Stanford JB, Warren G et al.: Increased Likelihood of Pregnancy Using an App-Connected Ovulation Test System: A Randomized Controlled Trial, J Womens Health 2020, funded by the manufacturer
- Johnson S, Bond S, Grace B, Marriott L: Increased Chance of Live Birth Following Use of Connected Ovulation Test System, Womens Health Rep 2022;3(1):60-66, funded by the manufacturer
- Robinson JE, Wakelin M, Ellis JE: Increased pregnancy rate with use of the Clearblue Easy Fertility Monitor, Fertil Steril 2007, funded by the manufacturer
- Behre HM et al.: Prediction of ovulation by urinary hormone measurements with the home use ClearPlan Fertility Monitor, Hum Reprod 2000
- Bouchard TP et al.: Validating ovulation prediction and confirmation with the Mira monitor: blinded ultrasound and serum hormone comparison, Reprod Biomed Online 2026
- Usala SJ et al.: Comparison of Day-Specific Serum LH, Estradiol, and Progesterone with Mira Monitor Urinary LH, Estrone-3-glucuronide, and Pregnanediol-3-glucuronide Levels in Ovulatory Cycles, Medicina 2024
Studies on temperature sensors, apps, and fertility trackers
- Shpaichler Y et al.: Accuracy of an Overnight Axillary-Temperature Sensor for Ovulation Detection: Validation in 194 Cycles, Sensors 2025, with manufacturer involvement
- Thigpen N, Patel S, Zhang X: Oura Ring as a Tool for Ovulation Detection: Validation Analysis, J Med Internet Res 2025, authors employed by Oura
- Favaro C et al.: Time to Pregnancy for Women Using a Fertility Awareness Based Mobile Application to Plan a Pregnancy, J Womens Health 2021, funded by the manufacturer
- Retraction Note: Improving usability and pregnancy rates of a fertility monitor by an additional mobile application (Daysy/DaysyView), Reproductive Health, 2019
- van de Roemer N, Haile L, Koch MC: The performance of a fertility tracking device, Eur J Contracept Reprod Health Care 2021, with manufacturer involvement
- Freundl G, Frank-Herrmann P, Bremme M: Results of an efficacy-finding study with the computer-thermometer Cyclotest 2 plus containing 207 cycles, Adv Contracept 1998
- Freis A et al.: Plausibility of Menstrual Cycle Apps Claiming to Support Conception, Front Public Health 2018
Package inserts and manufacturer information
