Ovulation Calculator

In a standard 28-day cycle, ovulation typically occurs on day 14 (counting from the first day of your period). However, the exact day varies by cycle length: ovulation usually happens 14 days BEFORE your next period, not 14 days after your last period. If your cycle is 30 days, you likely ovulate around day 16.

Sperm can survive in the reproductive tract for up to 5 days. An egg lives 12-24 hours after ovulation. Therefore, the fertile window is about 5-6 days: the 5 days before ovulation and the day of ovulation. Having sex during this window maximizes chances of conception.

Signs of ovulation: cervical mucus becomes clear and stretchy (like egg whites); mild one-sided pelvic pain (mittelschmerz); slight increase in basal body temperature (BBT) of 0.2-0.5°F; ovulation predictor kits (OPKs) detect the LH surge 24-36 hours before ovulation; breast tenderness; increased libido.

With perfect use, calendar/cycle tracking methods (NFP/FAM) are about 99% effective. Typical use is closer to 76-88% effective. These methods work best for women with very regular cycles. They are not recommended as sole contraception for those with irregular cycles. Combine with BBT charting and cervical mucus monitoring for better accuracy.

Irregular cycles make prediction difficult. Track your BBT (basal body temperature) daily to detect the temperature rise that confirms ovulation occurred. Use OPKs starting from your earliest possible ovulation day. Apps like Natural Cycles use BBT data with algorithms for more accurate predictions. Consider consulting a gynecologist for persistent irregularity.