Timing the Most Fertile Days

Conception is a window, not a moment: sperm survive about five days, the egg about one. This ovulation calculator predicts ovulation from your cycle and marks the fertile window — the days that matter most for conceiving.

The Calendar Method

The luteal phase — from ovulation to the next period — is remarkably consistent, typically 14 days. So ovulation falls cycle-length minus luteal days before the next period: in a 28-day cycle with a 14-day luteal phase, day 14.

Accuracy Notes

Calendar predictions assume regularity. For irregular cycles, supplement with ovulation predictor kits, basal-body-temperature tracking, or cervical-mucus observations — the calculator's date is a strong starting point, not a guarantee.