Finding Your Fertile Window

This fertility calculator predicts ovulation by counting back the luteal phase from your expected next period — ovulation happens about 14 days before menstruation in a typical cycle. The fertile window extends 5 days before ovulation through 1 day after, covering sperm survival and egg viability.

Why the Window Is Six to Seven Days

Sperm can remain fertile inside the reproductive tract for up to 5 days, while the released egg survives only about 24 hours. That asymmetry is why conception is most likely when intercourse happens in the days leading up to ovulation, not on ovulation day itself.

Confirming with Tracking

Cycle lengths shift month to month. Basal body temperature rises after ovulation, cervical mucus becomes clear and stretchy beforehand, and LH test strips surge 24–48 hours before release — combine a couple of these methods for the most reliable window.