Ovulation calculator

Enter the start date of your last period and your average cycle length: get your fertile days, ovulation day and next period. Everything stays on your device.

Last period start

Cycle length (days)

🌸 Fertile window

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🥚 Ovulation (most fertile day)

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📅 Next period

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How it works

Ovulation usually happens about 14 days before the next period. The fertile window covers the days most likely for conception: from 5 days before ovulation (sperm can survive up to 5 days) to the day after.

Please note

This is an estimate based on a regular cycle: the actual timing of ovulation can vary month to month. It is not a reliable contraceptive method. To plan or avoid a pregnancy, or if your cycles are irregular, talk to your doctor or gynecologist.