Ovulation and Period Calculator
Pick the first day of your last period and your cycle length. You get your ovulation day, fertile window and next period dates for the next three cycles.
How are fertile days calculated?
Ovulation usually happens about 14 days before your next period, whatever your cycle length. The fertile window is about 6 days: the 5 days before ovulation and ovulation day itself, because sperm can live up to 5 days and the egg about one day.
Example: your last period started on 1 October and your cycle is 28 days. Your next period is due on 29 October, so ovulation is around 15 October and your fertile days are 10 to 16 October.
The estimate is more accurate if your cycle is regular. Ovulation test strips can confirm it. This is not a reliable method of contraception.
Frequently asked questions
When do I ovulate?
How many fertile days are there in a cycle?
When should I take a pregnancy test?
Results are estimates for guidance and do not replace the official authority or professional advice.