Ovulation & Due-Date Calculator

Your fertile window and due date

This calculator estimates your most fertile days and ovulation from the first day of your last period and your average cycle length, or works out an estimated due date forty weeks on. Cycles vary, so treat the dates as a guide rather than a guarantee.

Estimates, not certainty

For trying to conceive or pregnancy care, your doctor or midwife is the right place for personal advice. Browse all our health guides for calm, plain-English information.