Health & Fitness

What Is the Fertile Window?

The fertile window is the time in a menstrual cycle when pregnancy is possible: typically the five days before ovulation plus the day of ovulation. It is based on how long sperm and an egg can survive. Calendar-based estimates assume ovulation occurs about 14 days before the next period.

How It Is Estimated

Estimated ovulation = expected next period − luteal phase length (commonly 14 days). The fertile window is the ovulation day and the five days before it.

Limitations

Ovulation timing varies from cycle to cycle, so calendar estimates are approximate and are not a reliable method of contraception.

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🌸 Ovulation Calculator Estimated fertile window, ovulation date, and next period. Calculate → 👶 Pregnancy Due Date Calculator Estimate your due date based on your last menstrual period. Calculate →

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Last updated: September 27, 2026. This definition is for general educational purposes only. It is not financial, investment, tax, legal, or medical advice, and it does not recommend any product or course of action. For decisions about your own situation, consult a qualified professional.