Pregnancy Due Date Calculator

Estimate your due date from the first day of your last menstrual period.

First day of last period

Average cycle lengthdays

Estimated due date

2026-10-08

Last updated: 2026-08-30

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FAQ

How accurate are due dates?

Only about 4% of babies arrive exactly on the estimated date; most are born within two weeks of it.

What is Naegele's rule?

Add 280 days (40 weeks) to the first day of the last period, adjusting for cycle length if it differs from 28 days.

Why does cycle length matter?

Ovulation happens about 14 days before the next period, so longer cycles shift conception and the due date later.

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