Ovulation Calculator

An ovulation calculator helps you find the days in your cycle when conception is most likely. Enter the first day of your last period and your usual cycle length (between 21 and 35 days), and the tool instantly estimates the ovulation date using the standard method: ovulation typically occurs about 14 days before the next period — the length of the luteal phase, which stays remarkably stable even when cycles differ in length.

Around the ovulation date, the calculator highlights the fertile window: the five days before ovulation plus the day itself. Sperm can survive in the body for up to five days, while the egg lives roughly 12–24 hours after release, so these six days are when pregnancy is realistically possible — with the highest chances in the last two or three days of the window.

Because plans rarely fit inside a single month, the tool also forecasts the next three cycles in a compact table: when each period is expected to start, the estimated ovulation day, and the fertile days for that cycle. The expected date of your next period is shown as well, which makes the calculator equally handy for planning a pregnancy or simply keeping track of your calendar.

Everything runs locally in your browser — no accounts, no uploads, and no stored data, so intimate information stays with you. Keep in mind that calendar methods are estimates: stress, travel, or illness can shift ovulation, and irregular cycles make predictions less reliable. This is an approximate calculation, not medical advice — for contraception decisions or fertility concerns, please talk to your doctor.