Ovulation Calculator

First day of last period

Please select the first day of your last period.

Average cycle length (days)

Please enter a cycle length between 21 and 45 days.

Ovulation timing varies. This tool is for informational purposes only. Consult your doctor for fertility advice.

Your Fertile Window

FAQs

When does ovulation usually happen?

In an average 28-day cycle, ovulation often happens about 14 days before the next period, but real cycles vary. It may not happen on the exact same day every month.

What is the fertile window?

The fertile window usually includes the five days before ovulation, the day of ovulation, and sometimes the day after ovulation, because sperm can survive for several days and the egg survives for a shorter time after release.

Is the ovulation calculator accurate for irregular periods?

It is less accurate if your cycle length changes often. People with irregular cycles may need ovulation predictor kits, cervical mucus tracking, basal body temperature tracking, or medical advice.

What cycle result may suggest I should speak to a doctor?

Very irregular cycles, missed periods, cycles consistently shorter than 21 days or longer than 35–45 days, or difficulty conceiving after trying may be worth discussing with a healthcare professional.