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Pregnancy Due Date Calculator

Due Date from Last Period

Calculate due date from the first day of your last menstrual period (Naegele's rule)

Formula

Due Date = LMP + 280 days (40 weeks)

Frequently Asked Questions

How is a due date calculated?
Using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14.
How accurate is a due date calculator?
Due date calculators give an estimate. Only about 5% of babies are born on their exact due date. About 80% are born within 2 weeks of the estimated date.

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