Last updated: March 2, 2026

When Is Your Baby Due?

Formula

Pregnancy typically lasts about 280 days (40 weeks) from the first day of your last menstrual period. Naegele's rule estimates the due date by adding 280 days to the LMP date.

Only about 5% of babies arrive on their exact due date. Most are born within two weeks before or after. Your healthcare provider may adjust the date based on ultrasound measurements.

Common use cases:

  • Tracking pregnancy milestones
  • Planning maternity leave
  • Preparing for delivery

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