Best Period and Ovulation Tracker App: 7 Compared (2026)
Some apps measure ovulation and some estimate it from your period dates. Here are seven, sorted by which is which.
The best period and ovulation tracker app depends on how it finds ovulation: Natural Cycles works it out from your temperature, Premom reads ovulation test strips, Fertility Friend charts both for free, and Clue, Flo and Apple Health estimate it from your period dates. It is very common to start with a calendar app and learn later that its ovulation day is an estimate. This guide compares seven apps by method, price and who each one fits.
What is the best period and ovulation tracker app?
The best period and ovulation tracker app is one that logs your periods and also finds your fertile days by a method that suits your goal. For trying to conceive, that means ovulation tests or temperature, as in Premom, Natural Cycles and Fertility Friend. For understanding your month, a calendar app such as Clue, Flo, Apple Health or Otty is enough.
The method matters because the window is short. ACOG says you can become pregnant from sex anywhere from 5 days before ovulation until 1 day after. An app that only knows your period dates has to assume where those days fall.
So this comparison sorts the apps by how they find ovulation first and by brand second.
How does an ovulation tracker app find ovulation?
An ovulation tracker app finds ovulation in one of four ways: counting days from your period dates, reading ovulation test results, tracking your basal body temperature, or combining several signs on one chart. Counting days predicts ovulation ahead of time with the least certainty. Tests and temperature read what your body is doing this cycle.
– Calendar, from period dates only. A calendar tracker counts back from your next expected period. The Office on Women’s Health says the time before ovulation varies from 13 to 20 days, between people and from month to month in the same person.
– Ovulation tests. Test strips detect the hormone LH in urine. Cleveland Clinic says a positive result means you are about to ovulate, usually within 36 hours.
– Temperature. The same Office on Women’s Health page says basal body temperature usually rises by 0.4 to 0.8 degrees Fahrenheit with ovulation. The rise shows that ovulation has happened, so it confirms the day afterward.
– Charting. Temperature and cervical mucus go on one chart, often with test results. ACOG calls the combination the symptothermal method.
The research on calendar-only prediction points one way. A 2018 study of 949 volunteers measured LH to find each person’s real ovulation day, and apps working from cycle length were right no more than 21% of the time. An earlier test of 20 websites and 33 apps found that one website and three apps predicted the precise fertile window for a standard 28-day cycle.
Our guide to how accurate period tracker apps are walks through that research, and what ovulation is covers the biology behind it.
Best period and ovulation tracker apps at a glance: 7 compared
These are the seven apps side by side, with the method each one uses and what it costs in the United States. Each one also tracks periods.
The sections below take them in order of how directly they measure ovulation.
Natural Cycles: the best ovulation tracker app if you measure temperature
Natural Cycles is a temperature-based app. The FDA cleared it as birth control, and its NC° Plan Pregnancy mode uses the same measurements to track ovulation when you are trying to conceive.
Its App Store listing says the algorithm updates your fertility status every day from your temperature trend. You can measure with its own NC° Band, a basal thermometer, an Oura Ring, WHOOP, compatible Garmin devices or an Apple Watch Series 8 or newer. The Plan Pregnancy page adds optional ovulation tests and a partner view.
It is also the most expensive app here, at $21.99 a month or $149.00 a year, and the listing says the annual plan comes with an NC° Band. Pick it if you want ovulation measured every cycle and you will take a temperature every night. If you are weighing it against a calendar app, Natural Cycles vs Flo sets the two methods side by side.
Premom: the best app to track ovulation with test strips
Premom is a free ovulation tracker app built around ovulation tests. Its App Store listing says you scan a test strip with your phone, Premom turns the line into an LH level, and you get a fertility reading of low, high or peak.
The period calendar then adjusts to your test and temperature data, so it is not working from dates alone. The listing also describes a thermometer that syncs to Premom, temperature import from Apple Health, and a companion app called Predad that lets a partner follow along. Premom describes itself as free, and Premom Premium adds advanced cycle reports and extra content.
Premom fits anyone who wants to see the LH surge for themselves. It also suits irregular cycles, where a calendar estimate has the least to go on, and our PCOS period tracker comparison covers that case.
Fertility Friend and Apple Health: the free ways to confirm ovulation
Fertility Friend is a charting app. You enter your temperature, cervical fluid and ovulation test results, and the free version builds the chart, highlights the fertile window and detects when ovulation likely occurred.
Its listing states that it does not sell or share your data or display ads, and that it imports temperatures from Apple Health and Oura. The optional VIP membership adds deeper analysis at $10.99 for 30 days or $45.99 a year. It asks for a daily entry, so it suits people who like seeing the chart build.
Apple Health’s Cycle Tracking is already on your iPhone and costs nothing. Apple says its fertile window prediction is based on a traditional calendar method, and a positive ovulation test you log can shift that window.
An Apple Watch changes what it can do. Apple Watch Series 8 or later uses wrist temperature to estimate the day ovulation likely occurred, after it has happened, once you have worn the watch to sleep for at least two cycles. Apple also states that Cycle Tracking should not be used as a form of birth control, and our Apple Health period tracker review covers the rest of it.
Clue and Flo: calendar predictions inside a full period tracker
Clue and Flo are period trackers first. Both predict ovulation and the fertile window from the period data you log, which makes them the easiest to use and the least exact on the day.
Clue’s App Store listing describes Clue Conceive mode as a medical device feature that predicts fertile days as an aid for conception. Clue’s own page says it needs only your period start dates and shows a wider range of days because ovulation moves from cycle to cycle. Clue Conceive is part of Clue Plus, at $9.99 a month or $39.99 a year, and the same listing says Clue is not intended for contraceptive purposes.
Flo’s listing describes fertile window and ovulation predictions based on your logged period data. You can also log ovulation test results and basal body temperature in it, and Flo sells a Premium subscription on top of the free app.
Choose either one if you mainly want a period tracker with symptoms and reminders. Our best period tracker app comparison covers both in more depth.
Otty: the period and ovulation calendar for two people
Otty is our own calendar tracker, so Otty sits in the estimate group and is not a fertility tool. You log the day your period starts, and the calendar paints the month in five phases. You see an estimated ovulation day on that calendar, and the Today screen counts down to it.
Otty does one thing beyond dates. If you log ovulation tests or temperature in Apple Health, Otty reads them and marks that cycle’s ovulation day as confirmed from Apple Health. Otty only reads from Health and writes nothing back.
Where Otty fits is the second person. If you pair with a partner, both phones show the same calendar, including the fertile phase Otty calls Glow, and your partner gets one specific thing to do each day. You can keep a test-based app for the measuring and use Otty for the calendar you share.
Otty is on iPhone only, has no test-strip reader and no temperature chart, and is not a contraceptive. Each person subscribes after the 7-day free trial, at $5.99 a month or $39.99 a year. Our best period tracker for couples comparison has the full field of two-person apps.
How do you choose an ovulation tracker app?
Choose an ovulation tracker app by matching its method to your goal: if you are trying to conceive, pick one that reads ovulation tests or temperature. If you are avoiding pregnancy, only an app cleared as birth control counts, used exactly as directed. If you want to understand your month, a calendar app is enough.
Once you have picked, a few habits make any of these apps more useful.
- Log every period start, because every method here builds on it.
- Add ovulation tests or temperature when the exact day matters to you.
- Give a new app a few cycles of data before you judge it.
- Use a calendar estimate as birth control.
- Treat a predicted ovulation day as a measured one.
- Assume your cycle is 28 days with ovulation on day 14.
That last one catches a lot of people. In a study of 612,613 tracked cycles, 13% were exactly 28 days long. The NHS puts the time from ovulation to the next period at around 10 to 16 days, so even the second half of the cycle is a range.
When should you see a doctor about ovulation or trying to conceive?
An ovulation day that moves by a few days from one cycle to the next is expected, and an app that shows a different day each month is working as designed.
The Office on Women’s Health says it is worth talking to a doctor in these cases:
– You have been trying to get pregnant for one year, or for six months if you are 35 or older.
– Your periods are irregular or have stopped.
– Your periods are very painful.
– You have endometriosis, pelvic inflammatory disease, or more than one miscarriage.
The same page says it is a good idea to talk to a doctor before you start trying. If you go, take your app with you, because a few months of logged periods, test results or temperatures gives the appointment something concrete to start from.
