Baby & family
Ovulation Calculator
Estimate your most fertile days for the next three cycles from the first day of your last period and your usual cycle length.
Estimated ovulation day
—
| Cycle | Fertile window | Ovulation |
|---|
Estimates assume a regular cycle and ovulation about 14 days before your next period. Real cycles vary. Not for use as birth control, and not medical advice. Ovulation tests or your doctor can give a better picture.
How it's calculated
Fertile window ≈ 5 days before ovulation through ovulation day
Worked example
How the fertile window works
Ovulation usually happens about 14 days before your next period, so with a 28-day cycle that's around day 14, and with a 32-day cycle around day 18. Sperm can live up to about 5 days, and the egg about a day, so the fertile window is roughly the 5 days before ovulation plus ovulation day itself. The 2 days before ovulation are usually the most fertile.
Next steps: estimate your due date or, just for fun, try the Chinese & Mayan gender predictor.