Period Calculator
Estimate your upcoming period dates and fertile window with one entry. Add the first day of your last period, your average cycle length and usual period length — the calendar shows your next three predicted periods and ovulation estimates instantly.
Enter your details above and the result will appear here.
How to use
- Enter the first day of your last period.
- Enter your average cycle length and usual period length.
- Your next three predicted periods appear instantly.
Note
Predictions add your average cycle length repeatedly, and ovulation is estimated as 14 days before the next period. Cycles naturally vary by a few days, and stress, illness and travel shift them — predictions get less accurate further ahead and with irregular cycles. Estimate only — not medical advice.