Ovulation Calculator

Understanding your menstrual cycle and identifying your fertile window is useful for both planning a pregnancy and understanding your reproductive health. Ovulation — the release of a mature egg from the ovary — typically occurs around day 14 of a 28-day cycle, but varies significantly for most women.

The fertile window is approximately 5–6 days long: the day of ovulation plus the 5 days before. Sperm can survive in the reproductive tract for up to 5 days, while an egg survives only 12–24 hours after ovulation. This is why timing intercourse in the days before ovulation — not only on the day of — maximizes the chance of conception.

How to identify ovulation: Basal Body Temperature (BBT) rises slightly (0.2–0.5°C or 0.4–0.9°F) after ovulation due to progesterone — tracking BBT daily over several cycles reveals your personal pattern. Cervical mucus changes from thick/creamy to clear, slippery, and stretchy (like raw egg white) as ovulation approaches — this is the most fertile sign. Ovulation predictor kits (OPKs) detect the LH surge that occurs 24–36 hours before ovulation; positive OPK = ovulation is imminent. Mittelschmerz (ovulation pain): some women feel a brief, one-sided pelvic twinge at ovulation.

Cycle length and its effect on timing: ovulation occurs approximately 14 days BEFORE the next period, not 14 days after the last. In a 35-day cycle, ovulation occurs around day 21. In a 24-day cycle, around day 10. This is why cycle length matters for predicting ovulation timing accurately.

Calendar-based methods (including this calculator) are estimates based on averages and are not suitable for contraception. They're most useful as a starting framework alongside other fertility tracking methods for women trying to conceive.