Ovulation Calculator

Ovulation typically happens about 14 days before your next period, not 14 days after the start of your last one. That distinction matters a lot if your cycle is not exactly 28 days. For a 32-day cycle, ovulation falls around day 18, not day 14. For a 26-day cycle it falls around day 12. The luteal phase (ovulation to next period) stays roughly constant at 14 days for most women; what varies is the follicular phase before ovulation.

The egg lives for 12-24 hours after release. Sperm can survive in fertile cervical mucus for up to 5 days. That gives you a fertile window of roughly 6 days: 5 days before ovulation through to the day of ovulation itself. The 2-3 days immediately before ovulation are the most fertile because mucus is most welcoming and sperm have time to travel.

A calendar prediction is a starting point, not a guarantee. To confirm ovulation has actually happened, watch for three signals. Cervical mucus shifts from creamy and sticky to clear, slippery, and stretchy (resembling raw egg white) in the days leading up to ovulation. Basal body temperature, taken first thing every morning before getting out of bed, rises by 0.2-0.5C the morning after ovulation and stays elevated until your period starts. Ovulation predictor kits (OPKs) detect the LH surge 12-36 hours before the egg releases.

If you are trying to conceive, intercourse every 2-3 days throughout your fertile window is more effective than trying to time a single perfect day. Sperm need to be present and waiting when the egg releases, not racing to catch up. If you have been trying for 12 months without success (or 6 months if you are over 35), please see your GP. The NHS offers fertility investigations through your GP referral. If your cycles are unpredictable, the [irregular cycle ovulation estimator](/irregular-cycle-ovulation-estimator) handles variable cycle lengths better than this one.