Period Cycle Tracker
Enter your cycle details once — get your next three periods, your fertile window, estimated ovulation day and a highlighted calendar. Private: everything stays in your browser.
Your cycle details
Enter your most recent earlier starts, newest first. The tracker averages the gaps between them.
Today in your cycle
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Cycle day
Next periods and fertility
Fertile window (next cycle)
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Estimated ovulation day
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Cycle calendar
Period days
Fertile window
Ovulation day
How to use
- Pick the date your last period started and check your average cycle and period lengths.
- For better predictions, add up to 6 earlier cycle start dates — the tracker auto-averages them.
- Everything updates instantly: today cycle day, next 3 predicted periods, fertile window, ovulation and PMS window.
- Your entries save automatically on this device. Use Clear all my data any time to remove them.
Privacy note: this tool works fully in your browser — no account, no uploads, nothing leaves your device. Predictions are estimates based on averages; they are not medical advice.