Ovulation Calculator

The calculator estimates your ovulation date by subtracting 14 days from your expected next period (which is your last period date plus your cycle length). Your fertile window is the 5 days leading up to ovulation plus the day of ovulation itself — a total of 6 days when pregnancy is most likely.

Your fertile window refers to the roughly 6 days each menstrual cycle when conception is possible. This includes the 5 days before ovulation and the day of ovulation itself. An egg can only be fertilized for 12–24 hours after release, but sperm can survive in the reproductive tract for up to 5 days, which is why this window spans multiple days.

For a typical 28-day cycle, ovulation usually occurs around day 14. However, every woman is different — ovulation generally happens about 14 days before the start of the next period, regardless of how long your cycle is. For a 32-day cycle, for example, ovulation would fall around day 18.

Common signs include a slight rise in basal body temperature (BBT), changes in cervical mucus (it becomes clearer and more slippery, similar to raw egg whites), mild pelvic or lower abdominal pain (mittelschmerz), and increased sex drive. Some women also use ovulation predictor kits (OPKs) that detect the LH surge preceding ovulation.

The best approach is to have unprotected sex regularly during your fertile window — especially in the 2–3 days just before your estimated ovulation date. Maintaining a healthy weight, avoiding smoking and excessive alcohol, reducing stress, and taking a prenatal folic acid supplement can also support fertility.

No. This calculator should not be used as a form of birth control. Ovulation timing can vary from cycle to cycle due to stress, illness, travel, or hormonal changes, making it unreliable as contraception. Talk to your healthcare provider about effective birth control options.

If your periods are irregular, this calculator's estimates will be less reliable since it assumes a consistent cycle length. In that case, tracking basal body temperature, monitoring cervical mucus, or using ovulation predictor kits can give more accurate day-to-day information. Consulting a healthcare provider is recommended.

The average menstrual cycle is 28 days, but a normal cycle can range from 21 to 35 days in adults. The length is measured from the first day of one period to the first day of the next. Cycle length can vary month to month even in people who are generally regular.