Ovulation Calculator

Ovulation & Fertile Window Calculator

Find your estimated ovulation day and most fertile days from the first day of your last period.

This is a general estimate based on cycle averages and is not medical or contraceptive advice. Ovulation timing varies; talk to your healthcare provider for fertility guidance.
On your journey? Try our due date calculator and browse pregnancy pillows & maternity care.
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How the fertile window works

Ovulation usually happens about 14 days before your next period. Your fertile window is roughly the 5 days before ovulation plus ovulation day, because sperm can survive a few days. This tool assumes a regular cycle.