Flo, Clue, Leap Period Calendar and My Calendar compared — period predictions, symptom logs, pregnancy tracking and how each handles sensitive health data.
A cycle tracker earns its place in two moments: predicting when the next period starts, and turning months of symptoms into a pattern worth showing a gynaecologist. Predictions sharpen with every logged cycle, while symptom notes reveal the headaches, skin changes or mood shifts that keep arriving in the same phase. Because this is particularly sensitive health data, the third decision is privacy — an anonymous mode, European privacy law, or an app that never asks you to register at all. The app reviewed in depth below is the global market leader; the FAQ compares it with European and no-account alternatives on accuracy and data handling.
Flo is the world's most used period tracker, with period and fertile-day predictions, detailed symptom logging, week-by-week pregnancy tracking and an anonymous mode.
Trusted by over 460 million people, it forecasts periods, fertile windows and ovulation, and those forecasts narrow as months of logged cycles accumulate. Beyond the calendar it records symptoms in detail and follows pregnancy week by week, with more than 100 health professionals involved in its content; anonymous mode separates health entries from your identity. The cost story is the main weakness: the most useful features sit behind Premium, upselling is persistent, and users repeatedly report free functions disappearing in updates, so treat the free tier as a trial of the core calendar.
Pros
100M+ downloads, the world's most used tracker
Week-by-week pregnancy tracking
More than 100 health professionals on the team
Cons
Most useful features are paywalled
Aggressive upselling to Premium
Users report free features removed in updates
Download price only. In-app purchases and subscriptions may cost extra.
Questions & answers
Are period predictions actually reliable?
The more regular your cycle and the more months of data the app has, the sharper they get: with regular cycles they land within 1-2 days. Irregular cycles make predictions much less dependable, and there the value lies in the log — something concrete to show your gynaecologist — rather than the forecast. No app on its own works as a reliable contraceptive method, and none should be treated as one.
What about the privacy of my period data?
It is the right question to ask: this is sensitive health data. Flo offers an anonymous mode that separates your data from your identity, while Clue is based in Europe, in Germany, under GDPR and has a public record of refusing to hand data over. Simple apps with no sign-up, such as Leap's calendar, keep entries on the phone. Always check whether registration is optional and skip the account if you do not need syncing.
Why log symptoms and not just dates?
To uncover your own patterns: headaches that always arrive two days early, mood swings around ovulation, skin flare-ups in the luteal phase. Seeing it in black and white over several cycles lets you plan ahead and tell what is normal for you from what is not. A symptom log covering months is also genuinely useful for a gynaecologist if you consult about irregularities, severe pain or fertility.
More related apps
App library · United States App Store. Prices and availability reflect the last check.
