Pregnancy Due Date Calculator

First day of the last period in, estimated due date out — Naegele's rule, 280 days, shown plainly.

Example — Last period started January 15, 2026Estimated due date: Thursday, October 22, 2026

First day of last period

How we got it — the example, step by step

The standard estimate counts 280 days (40 weeks) from the first day of the last period.
January 15, 2026 + 280 days = October 22, 2026.

Check it backwards

Count back: October 22, 2026 minus 280 days is January 15, 2026 — the date we started from.

Questions people also ask

How exact is a due date?
It is an estimate. Only about 1 in 20 babies arrive on the estimated date itself, and a date from an early scan replaces this rule-of-thumb when a clinician gives one. This page plans calendars; it does not give medical advice.

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Every answer on this page is computed, not typed from memory — the check under each result runs the calculation backwards. Figures are rounded only where the page says so. Last updated: October 13, 2026 · Clirto — every answer free, every step shown.