Health tool
Ovulation Calculator
Estimate your next ovulation date and fertile window from your last period and typical cycle length.
—Estimated ovulation day
—Fertile window
—Next expected period
How this estimate works
Ovulation typically happens about 14 days before the next period starts, regardless of total cycle length. The fertile window covers the 5 days before ovulation plus ovulation day itself, since sperm can survive that long. Cycles vary naturally, so treat this as a general estimate rather than a precise prediction — tracking a few real cycles improves accuracy.