Ovulation Calculator

Estimate ovulation day and your fertile window from cycle length.

This cycle

Est. ovulation
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    Educational estimate only — not medical advice and not a contraceptive method. Cycles and ovulation timing vary. Consult a clinician for fertility or contraception guidance.

    How to use this ovulation calculator

    1. Enter the first day of your last period.
    2. Enter your average cycle length.
    3. Review estimated ovulation and fertile days.

    FAQ

    Why estimate from next period − 14?

    The luteal phase is often ~14 days. Follicular phase length varies more with cycle length.