Ovulation Calculator
Predict your ovulation date and fertile window from your last menstrual period.
Ovulation typically occurs 14 days before your next period. The fertile window spans 6 days around ovulation.
How the Ovulation Calculator Works
This calculator estimates your ovulation date, fertile window, and next period based on the first day of your last menstrual period (LMP) and your average cycle length.
It assumes ovulation occurs 14 days before your next expected period, since the luteal phase length is fairly consistent across cycles. The fertile window is calculated as the 5 days before ovulation plus the day of ovulation, accounting for sperm viability and egg lifespan.
Example: With an LMP of June 1 and a 28-day cycle, ovulation is estimated around June 15, with a fertile window from June 10 to June 16, and the next period due around June 29.