What is a period tracking app?
A period tracking app is a phone app that records the dates of your periods, and often symptoms, mood and body signs, to estimate when your next period, fertile window and ovulation are likely. Most use the average of your past cycles; some add temperature or ovulation test data. Predictions are estimates, not medical tests or contraception.
What period tracking apps do
- Predict your next period from your average cycle length
- Estimate your fertile window and ovulation day
- Log flow, symptoms, mood, sex, temperature and notes
- Show patterns, like PMS that arrives on the same cycle days
- Create a summary to bring to a doctor
How accurate are they?
With regular cycles, period predictions are usually close. Ovulation estimates from dates alone are less precise, because ovulation day varies even in regular cycles. Adding basal body temperature, wrist temperature or LH tests improves the picture. See how accurate are period trackers and how period trackers predict.
Questions to ask about privacy
| Question | Why it matters |
|---|---|
| Where is my cycle data stored? | on your phone only, or on the company's servers |
| Do I need an account? | accounts usually mean data is held in the cloud |
| Is data shared with advertisers or analytics firms? | some apps have shared health data in the past |
| Can I export or delete everything? | your data should stay yours |
Read more in is my period tracker private and do period apps share data.
Lulu keeps your cycle data on your iPhone with no account, predicts your period and fertile window, and learns how you usually feel in each phase from one-tap mood check-ins. It is a tracker, not a diagnosis tool and not contraception.
Mood tracking in period apps
Some apps add mood tracking, which can reveal whether your harder days cluster before your period, a pattern worth sharing with a doctor if you suspect PMDD.
Frequently asked questions
Can a period tracking app be used as birth control?
Only a few apps are cleared as contraception, and they require strict daily temperature use. Most period trackers, Lulu included, are not contraception.
Do period apps work with irregular cycles?
They can still log and show patterns, but predictions are wider. See do period apps work with irregular cycles.
Sources
- Office on Women's Health: Your menstrual cycle
- Worsfold L et al. Period tracker applications: what menstrual cycle information are they giving women? Womens Health (2021)
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
Best period tracker apps: an honest comparison for 2026The best period tracker app depends on you. Flo, Clue, Apple Cycle Tracking, Natural Cycles, Stardust, Maya and Lulu compared on features, privacy and price.Are period trackers accurate? What they get right and wrongAre period trackers accurate? Usually within a few days for your next period, much less for ovulation. What drives accuracy and how to read your app wisely.
Is my period tracker private? How to choose a safe oneLooking for the safest period tracker app? 6 checks to see if your tracker is private: storage, accounts, trackers, sharing and deletion. Plus how Lulu works.Period trackers that don't share your data: how to choose a private oneWant a period tracker without data sharing? How period apps handle your data, what went wrong at Flo, Maya and Stardust, and how to check any app yourself.
What is mood tracking?Mood tracking means recording how you feel each day to spot patterns. How it works with your menstrual cycle, and why doctors ask for it for PMS and PMDD.