Free tool
Ovulation calculator
Quick answer
Ovulation usually happens about 14 days before your next period. Enter your last period and cycle length to estimate your fertile days. This is for planning a pregnancy: calendar methods are among the least reliable ways to avoid one.
Your answers stay on this device.
For planning a pregnancy, not for avoiding one
Calendar-based methods are among the least reliable ways to avoid pregnancy: about 12 in 100 people get pregnant in a typical year. Compare methods
Educational only. Talk to a doctor or pharmacist if unsure.
How it works
We estimate ovulation as cycle length minus 14 days and the fertile window as the 5 days before plus the day after. In typical use about 12 in 100 people relying on a calendar method get pregnant in a year.[src] See natural methods.
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This guide is for information. Talk to a doctor before starting, stopping or switching birth control.
Sources
- Family Planning: A Global Handbook for Providers, WHO and Johns Hopkins CCP