How PeriodTracks Works

Simple, science-backed estimates. No lab tests, no account, no data sent anywhere.

01
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Enter Your Last Period Date

We just need the first day of your most recent period — day 1 of bleeding, not spotting.

02
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Set Your Cycle Details

Tell us your average cycle length (default 28 days) and how long your period lasts. Adjust the luteal phase for more precision.

03
✨

Get Your Cycle Snapshot

Instantly see your predicted next period, ovulation day, fertile window, and a 3-month calendar — all calculated locally.

04
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Save & Plan Ahead

Download an ICS calendar file to add events to Google, Apple, or Outlook Calendar. No account required.

🔬 The Science Behind the Predictions

Next PeriodLast period start + Cycle length
OvulationNext period start − Luteal phase length
Fertile Window StartOvulation − 5 days
Fertile Window EndOvulation + 1 day

These formulas are based on the standard Ogino-Knaus calendar method. Accuracy improves when you track your cycle consistently over 3+ months.

⚠️ Important: PeriodTracks provides estimates only. Biological cycles naturally vary due to stress, illness, nutrition, and hormonal changes. This tool is not a substitute for medical advice. Consult a healthcare provider for concerns about your reproductive health.