Period Calculator and Calendar

Estimate your next period and bleeding dates for six cycles, with optional local history, JSON export and clear controls. Gregorian dates; estimates stay in your browser.

Cycle detailsData is saved only when you choose local storage.

First day of last period

Average cycle length

Period duration

Optional local historyIt stays in this browser and is never sent, but it is not encrypted on shared devices.

As-of date

All dates are Gregorian. Calculations run in your browser without sending your data.

An informational estimateCycles and ovulation can vary from month to month. Do not use these results for contraception or diagnosis.

Health reference ↗

ACOG ↗

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