Predict Ovulation

Estimate your fertile window and ovulation day.

Last Period Start Date

Cycle Length (days)

Ovulation Day

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Fertile Window

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The Methodology

LMP + Cycle Length - 14

This tool uses the verified professional formula shown above. We cite our sources so you can trust every result.

How it works

This tool identifies your "fertile window" by subtracting 14 days from your expected next period date. Sperm can survive for several days inside the body, so the fertile window starts a few days before ovulation.