Free calculator

Ovulation & Fertile Window Calculator

Estimate ovulation and a fertile window from your cycle. Calendar estimates are not a reliable contraceptive method.

What you get

Estimate an indicative ovulation window from your cycle information.

How to use it

Enter only the requested values and check the unit shown beside each field. The main result gives the figure to use first. Details explain conversions, secondary quantities and rounding. Change any value to compare another situation without starting again.

Before using the result

The dates are calendar estimates. Cycles and pregnancies vary between people, so the result cannot confirm ovulation, pregnancy or any medical condition.