Formula guide

Pregnancy Due Date Calculator formula

The standard due date estimate adds 280 days, or 40 weeks, to the first day of the last menstrual period. This is a common medical convention for estimating a due date in uncomplicated pregnancies.

How the input values are used

First day of last period

The calculation uses this date as a reference point; check whether endpoints are included.

How to interpret the result

  • The result uses First day of last period. Change one variable at a time to compare its effect on the outcome.
  • Health and fitness values are estimates, not a substitute for measurements or clinical advice.
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