Pregnancy Due Date Calculator

Based on Naegele's rule

This estimates a due date as 280 days (40 weeks) from the first day of your last menstrual period — the standard rule of thumb used as a starting estimate, first described by German obstetrician Franz Naegele in the 1800s.

It's a general estimate, not a substitute for dates confirmed by an ultrasound or your healthcare provider — actual delivery timing varies for plenty of normal reasons.