Ovulation calculator: fertile days

Enter the first day of your last period and your cycle length. You'll get the estimated ovulation, fertile window and next periods.

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Your numbers

The day the last period started.
Days from the start of one period to the start of the next. The average is 28.

The result updates as you type.

Result

Fill in the fields to see the result.

For general information only. It is not medical advice; for a personal answer, talk to a doctor or a dietitian.

Questions and answers

How is ovulation estimated?

Ovulation usually happens about 14 days before the next period. The fertile window is the 5 days before it and the day after.

Can I rely on it to avoid pregnancy?

No. Cycles vary, so this is only an estimate. For contraception or fertility questions, talk to a doctor.

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