Ovulation Calculator
Estimate your ovulation date and fertile window to help with planning a pregnancy. Enter the first day of your last period and your average cycle length to see your predicted ovulation day, most fertile days and next period.
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Please select the first day of your last period.
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Save ⟶How to use the Ovulation Calculator
- 1Enter the first day of your last menstrual period.
- 2Enter your average cycle length (commonly 28 days).
- 3Read your estimated ovulation date and your most fertile days.
- 4Plan around the fertile window, which spans the ~5 days before ovulation plus ovulation day.
Understanding your fertile window
Ovulation — when an ovary releases an egg — typically happens about 14 days before your next period starts. The fertile window is the roughly six days ending on ovulation day, because sperm can survive up to five days while the egg lives for about 24 hours. Timing intercourse in the days leading up to ovulation gives the best chance of conception.
This calendar method assumes a regular cycle. Real cycles vary, so combine the estimate with signs like basal body temperature, cervical mucus changes or ovulation predictor kits for greater accuracy.
Frequently Asked Questions
▸When am I most fertile?
In the five days before ovulation and on ovulation day itself, with the two days before ovulation usually the most fertile.
▸How accurate is an ovulation calculator?
It's a useful estimate for regular cycles but can't account for month-to-month variation. Tracking ovulation signs or using predictor kits improves accuracy.