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Pregnancy Due Date Calculator — How Many Weeks Pregnant Am I?

Estimate your due date from the first day of your last period (adjusted for cycle length) or from the conception date, see how far along you are, and the dates of key milestones.

Calculate from

First day of last period

Cycle length (days)

Estimated due date

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Milestones

Only about 1 in 25 babies arrive on the due date — most come within two weeks either side. An early ultrasound gives the most accurate date; follow your doctor or midwife.

How the due date is calculated

Naegele's rule: first day of the last period + 280 days (40 weeks).
Longer or shorter cycles move the date: a 32-day cycle adds 4 days.
From conception: + 266 days (38 weeks).

Frequently asked questions

Why do weeks count from my last period?

It's the standard medical convention — the first two “weeks” happen before conception.

Pregnancy Due Date Calculator — How Many Weeks Pregnant Am I?

Milestones

How the due date is calculated

Frequently asked questions

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