Calculators

Ovulation Calculator

Estimate your fertile window & ovulation.

First day of last menstrual periodAverage cycle length (days)

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estimated ovulation date

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Fertile window

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Peak (most fertile) days

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Next period

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Estimated due date if you conceive this cycle

Next 6 cycles

Cycle	Ovulation	Fertile window

This free ovulation calculator estimates your most fertile days and next period from the first day of your last menstrual period and your average cycle length. Ovulation is estimated at about 14 days before your next period, with the fertile window spanning the five days before ovulation through the day after. These are estimates based on cycle averages and can shift from month to month — they are a guide, not a reliable form of contraception.