Ovulation Calculator

About the Ovulation Calculator

Ovulation is the release of a mature egg from the ovary and typically occurs 14 days before the start of the next period — regardless of cycle length. This is why the formula used here is: Ovulation = LMP + (Cycle Length − 14). For a standard 28-day cycle, ovulation falls on day 14; for a 32-day cycle, it falls around day 18; for a 24-day cycle, around day 10. The fertile window spans 6 days: from 5 days before ovulation through 1 day after. The highest probability of conception comes in the 2–3 days immediately before ovulation. To estimate when conception likely occurred during a past cycle, try our Conception Calculator.

These calculations assume a consistent cycle length, but in reality, cycles can vary by several days from month to month. Stress, illness, travel, weight changes, and hormonal fluctuations can all affect when ovulation occurs. For this reason, calendar-based methods are best used as a starting point and combined with other indicators such as basal body temperature (BBT) charting, ovulation predictor kits (OPKs), or monitoring cervical mucus changes (which becomes clear and stretchy — resembling raw egg whites — in the days leading up to ovulation). If you have confirmed pregnancy, use our Pregnancy Calculator to track gestational age and milestones.

Women with irregular cycles — including those with polycystic ovary syndrome (PCOS) or other hormonal conditions — may find that calendar-based ovulation prediction is less accurate. In such cases, OPKs or monitoring by a healthcare provider are more reliable. If you have been trying to conceive for 12 months without success (or 6 months if you are over 35), a fertility specialist can evaluate both partners and recommend appropriate next steps. For pregnancy planning once conception is suspected, our Due Date Calculator can help you estimate your due date from LMP, conception date, or IVF transfer.