Ovulation Calculator

Estimate when you’re most likely to ovulate and your most fertile days.

Usually 12–16; 14 if you don’t know.
Dates use your browser’s date picker.
–
Ovulation
Fertile window
Next period
Next cycles
Pregnancy test from
Work

Saved Calculations

Items you add are saved in this browser.

NameCalculationResultRemove

How Ovulation Is Estimated

Ovulation usually happens about 14 days before the next period (the luteal phase is fairly constant; the first half of the cycle is what varies). Sperm can survive up to 5 days, so the fertile window is the 5 days before ovulation plus the day after.

Ovulation ≈ LMP + cycle length − luteal phase

Worked Example

Tips

Cycles vary month to month, so calendar estimates are rough. Ovulation test kits, basal body temperature and cervical mucus tracking are more accurate. This isn’t reliable birth control. Information only; ask your provider for advice.