Your cycle, understood.
Your data, untouched.
FlowKeeper predicts your next period, ovulation, and fertile window from your own history — with honest, statistics-backed estimates. Everything lives on your phone. No account. No cloud. No subscription.
A complete tracker, nothing extra
Log what matters in a tap, see the patterns, and get gently reminded — all without handing your health data to anyone.
Calendar & logging
Tap any day to record flow, symptoms, mood, energy, pain, and notes. A color-coded month makes your cycle obvious at a glance.
Predictions & insights
Next period, ovulation, and fertile window — each with a confidence level. Plus cycle stats and symptom patterns over time.
Gentle reminders
Optional local notifications before your period or fertile window. Scheduled on-device — they never touch a server.
App lock
Protect your data with a passcode and Face ID / Touch ID. Auto-locks after a delay you choose.
Export & import
Generate a doctor-friendly PDF summary or export raw CSV — and import a CSV back to move your history to a new phone, even between iOS and Android.
A calm, considered look
One thoughtfully chosen accent, soft glass surfaces, and full light, dark, and system modes — a quiet interface that stays out of your way.
Three steps, then it just works
Log your days
Mark period days and anything you want to remember. Even a few cycles is enough to start.
FlowKeeper learns
A robust on-device model cleans your history and weighs recent cycles to estimate what's next.
Stay ahead
See predictions with a clear confidence level, and get a heads-up before your period or fertile window.
Snext = Slast + round(weighted avg of your cycles) ± Δ
Recent cycles count more. Outliers are filtered out. And the result is wrapped in an 80% confidence band sized to how regular you are — never a false single date.
Predictions you can actually trust
FlowKeeper uses robust statistics — medians, recency weighting, and outlier rejection — so one unusual month can't throw off your forecast.
- A confidence band, not a fake exact day
- One bad log can't poison the estimate
- Identical math on iOS & Android, locked by tests
It can't leak what it never collects
FlowKeeper has no servers and no account system. Your cycles are stored only in the app's local database on your device. Privacy isn't a policy here — it's how the app is built.
- No cloud sync or servers
- No account, email, or login
- No analytics, ads, or trackers
- No subscriptions — one-time purchase
Take back your cycle data
Available on iPhone today. Coming to Android soon.
Requires iOS 17 or later. Android 8.0+.