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LunWise

Ovulation calculator

Estimate your ovulation day and fertile window for the next three cycles, and when to start using ovulation tests.

Calculated on your device. Nothing you enter is sent or stored.

Enter the first day of your last period to see your dates.

How this calculator works

  • Ovulation is estimated about 14 days before your next expected period.
  • Research suggests nearly all pregnancies come from intercourse in the six days ending on ovulation day.
  • Start LH ovulation tests the day before your fertile window opens, at about the same time each day.

Also try the period calculator, or read how to tell when you're ovulating.

Questions and answers

How many days is the fertile window?

About six days, ending on the day of ovulation. This calculator also includes the day after estimated ovulation, to allow for uncertainty.

Can I confirm when I ovulated?

Yes. A positive LH test means ovulation is likely within about a day, and a sustained rise in your waking temperature confirms it happened. LunWise detects both when you log them.

Can I use this to avoid pregnancy?

No. Calendar estimates are not a reliable method of contraception.

Sources

  1. Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. New England Journal of Medicine, 1995.
  2. Bull JR, Rowland SP, Scherwitzl EB, et al. Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. npj Digital Medicine, 2019.

Estimates only. Not medical advice and not a method of contraception.