Ovulation Calculator

How Ovulation Timing Works The menstrual cycle has two phases separated by ovulation:

1. The follicular phase — from the first day of your period to ovulation (variable length)
2. The luteal phase — from ovulation to the next period (almost always 14 days)

Because the luteal phase is constant at ~14 days, ovulation always occurs approximately 14 days before your next period. For a standard 28-day cycle: ovulation on day 14. For a 32-day cycle: ovulation on day 18. For a 24-day cycle: ovulation on day 10.

Formula Used Ovulation Day = LMP + (Cycle Length − 14) Fertile Window Start = Ovulation Day − 5 Fertile Window End = Ovulation Day + 1 Next Period = LMP + Cycle Length

Why Is the Fertile Window 6 Days? Sperm can survive in the female reproductive tract for 3–5 days after intercourse. An egg survives for only 12–24 hours after it is released. This means conception is possible from 5 days before ovulation through about 1 day after. The two most fertile days are the day before ovulation and the day of ovulation itself.

Important Accuracy Limitations This calculator assumes a regular cycle. Irregular cycles make prediction unreliable. Stress, illness, travel, and hormonal changes can shift ovulation by several days. This tool is for educational purposes only — not a substitute for ovulation testing strips (LH tests) or medical advice. For reliable fertility tracking, consider basal body temperature (BBT) charting combined with ovulation predictor kits (OPKs).