Ovulation Calculator

The ovulation calculator predicts when ovulation is most likely to occur and identifies the fertile window — the days when conception is possible. Ovulation typically occurs 14 days before the next expected period

The calculator uses the standard published formula for ovulation calc. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

This calculator works with inches. You can enter values in the units shown — the calculator handles all conversions internally.

The core formula is: Ovulation day estimate = LMP + (cycle length − 14 days). Each step in the calculation is shown so you can verify the result manually.