From the first day of one period to the first day of the next.
14 for most people. Leave it if you're not sure.

Likely ovulation day

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Fertile window
Next period
Earliest pregnancy test
Due date, if you conceive this cycle

The next six cycles

Period startsFertile windowOvulation

How the ovulation calculator works

Already pregnant? Find your due date and week by week with the due date calculator.

Frequently asked questions

When am I most fertile?

In the five days before ovulation and on the day itself. Sperm can live for up to five days, and an egg for about a day, so the two or three days before ovulation give the best chance of pregnancy.

How is ovulation worked out?

Ovulation usually happens about 14 days before your next period starts. With a 28-day cycle that's day 14; with a 32-day cycle, day 18. The calculator counts from the first day of your last period and your usual cycle length.

How accurate is it?

It's an estimate based on regular cycles. Ovulation can move from month to month with stress, illness or travel. Ovulation test kits, cervical mucus and basal body temperature give a more exact picture.

Can I use it to avoid pregnancy?

No. Calendar methods alone are not reliable birth control. Talk to a doctor or a family planning clinic about contraception.