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Ovulation Calculator

Estimate your ovulation day and fertile window from your cycle.

How to use

  1. Enter the first day of your last period.
  2. Set your average cycle length.
  3. See the estimated ovulation date, fertile window and next period.

Frequently asked questions

How is ovulation estimated?

Ovulation typically occurs ~14 days before the next period, with the fertile window covering the 5 days before plus ovulation day.

How reliable is a calendar estimate?

Cycles vary, so treat it as a guide. Ovulation tests or temperature tracking pinpoint it better - and this method is not reliable contraception.

Is this medical advice?

No - for general information. See a clinician for fertility concerns.

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