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Ovulation Calculator
Discover your fertility window.
Understanding Ovulation and the Fertile Window
Ovulation is the release of an egg from the ovary, typically occurring once per menstrual cycle. For conception, timing intercourse during the fertile window significantly improves the probability. An egg survives 12–24 hours after release; sperm can survive 3–5 days.
Fertile Window Timeline
- Day 1: first day of menstrual period
- Day 14: typical ovulation for a 28-day cycle (varies by cycle length)
- Fertile window: 5 days before ovulation + ovulation day = 6 days total
- For non-28-day cycles: subtract 14 from cycle length to estimate ovulation day
Signs of Ovulation
- Cervical mucus change: clear, slippery, egg-white consistency — most reliable physical sign
- BBT rise: 0.2–0.5°C increase after ovulation — confirms ovulation occurred
- LH surge: detected by ovulation predictor kits 24–36 hours before ovulation
This calculator is for informational purposes only. Cycle-tracking methods are not contraception.
How accurate are ovulation calculators?
Calendar-based calculators estimate ovulation as a fixed number of days before the next period. They're moderately accurate for women with very regular cycles but less reliable for irregular cycles. For higher accuracy: combine calendar prediction with BBT tracking, ovulation predictor kits, and cervical mucus monitoring.
Can you ovulate more than once per cycle?
Typically no — once LH surges and an egg is released, hormonal feedback suppresses further ovulation in that cycle. Fraternal twins result from two eggs released in the same LH surge event. True multiple separate ovulation events in one cycle are extremely rare in humans.