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Ovulation Calculator

Fertile window and ovulation dates for 3 cycles.

days

How to use

  1. 1Enter the first day of your last period.
  2. 2Enter your average cycle length (usually 21–35 days).
  3. 3See your fertile window and likely ovulation day.
  4. 4Plan ahead with the next three cycles shown below.

Frequently asked questions

How is ovulation calculated?

Ovulation usually happens about 14 days before your next period. So with a 28-day cycle it's around day 14, and with a 32-day cycle around day 18.

What is the fertile window?

The 5 days before ovulation and the day of ovulation. Sperm can survive up to 5 days, so these are the days pregnancy is most likely.

Is this reliable for avoiding pregnancy?

No. Cycles vary, so calendar methods aren't reliable contraception. Talk to a doctor about safer options.

My cycles are irregular. Will it work?

It will be less accurate. Ovulation tests, basal body temperature tracking or a doctor's advice give better results with irregular cycles.

Is my data stored?

No. Nothing you enter is saved or sent anywhere.

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