Estimate your ovulation date and fertile window
Calendar-based estimate that assumes a regular cycle and a 14-day luteal phase; the fertile window is the 5 days before ovulation plus ovulation day. Ovulation timing varies from cycle to cycle, so this is not reliable for contraception or for diagnosing fertility problems. Talk to a doctor if your cycles are irregular or you have been trying to conceive for a year (6 months if over 35).
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Frequently Asked Questions
No. Ovulation Calculator is free, with no signup required, and nothing you enter leaves your browser.
Ovulation Calculator is built on published formulas and reference ranges from established health sources. We revisit it periodically as guidance evolves; the "Last reviewed" date above shows when that last happened. If something looks wrong, tell us with the feedback button in the bottom-right corner.