Ovulation calculator

Predict your fertile window, expected ovulation day and next period from the first day of your last period and your usual cycle length.

First day of last period

Cycle length (days)

Ovulation (most likely)—

Fertile window—

Next period (estimated)—

Estimated due date if conception—

FAQ

How is ovulation predicted?

Ovulation typically happens 14 days before the next period (luteal phase length). Cycle length minus 14 gives you the ovulation day from the start of your cycle.

What is the fertile window?

The 5 days before ovulation plus ovulation day itself. Sperm can survive in the reproductive tract for up to 5 days, so intercourse in this window can lead to conception.