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Health & Fitness

Ovulation Calculator

Estimate ovulation and a six-day fertile window from a regular menstrual cycle.

Calendar estimate only for regular cycles. Ovulation can vary; this is not contraception, confirmation of fertility or a pregnancy test. Irregular cycles require a different assessment.

Health & Fitness

Ovulation Calculator

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How it works

Expected next period equals the first day of the last period plus cycle length. Estimated ovulation is the next period minus luteal phase days. The window covers the five days before ovulation and the estimated ovulation day. Calendar estimate only for regular cycles. Ovulation can vary; this is not contraception, confirmation of fertility or a pregnancy test. Irregular cycles require a different assessment.

Good to know

Frequently asked questions

How do I use it?

Fill in the options and press “Calculate”. Check the result, then copy or download it.

How does it work?

Expected next period equals the first day of the last period plus cycle length. Estimated ovulation is the next period minus luteal phase days. The window covers the five days before ovulation and the estimated ovulation day.

Are there limitations?

Calendar estimate only for regular cycles. Ovulation can vary; this is not contraception, confirmation of fertility or a pregnancy test. Irregular cycles require a different assessment.

Is my data uploaded?

No. Everything is processed in your browser and nothing is sent to a server. No account is needed.

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