Ovulation Calculator

Most women ovulate about 14 days before their next period starts (the luteal phase). The fertile window is the 5 days before ovulation plus the day of ovulation — roughly a 6-day stretch where pregnancy is possible. This calculator uses your last menstrual period (LMP) and cycle length to estimate this window.

Calendar-based ovulation calculators are estimates. Even with regular cycles, ovulation timing can shift by 1–3 days due to stress, illness, or hormonal changes. For more precise tracking, combine the calendar method with basal body temperature (BBT) charting, ovulation predictor kits (OPKs), or cervical mucus monitoring.

Calendar-based ovulation calculators are less reliable when cycles are irregular. If your cycles vary by more than 7 days, consider tracking ovulation symptoms directly using OPKs, BBT, or fertility apps that combine multiple signals. We are launching a dedicated Ovulation Calculator for Irregular Periods soon.

The 2–3 days leading up to ovulation are the most fertile. Sperm can survive in the female reproductive tract for up to 5 days, while the egg only lives 12–24 hours after ovulation. So having intercourse a day or two before ovulation gives sperm the best chance to meet the egg.

Most women have cycles between 21 and 35 days, with 28 days being the textbook average. Anything within that range is generally considered normal. Cycles shorter than 21 days or longer than 45 days may warrant a discussion with your healthcare provider.

Yes, but accuracy may be reduced for the first 1–3 months as your body re-establishes its natural cycle. Hormonal birth control suppresses ovulation, so your normal cycle pattern may take a few months to return.