Due Date Calculator

The estimated due date (EDD) is the predicted date of a baby's birth, typically calculated as 40 weeks (280 days) from the first day of the last menstrual period (LMP) — known as Naegele's rule. The actual birth normally occurs between 37 and 42 weeks gestation

The calculator uses the standard published formula for due date. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

This calculator works with percentages. You can enter values in the units shown — the calculator handles all conversions internally.

The core formula is: Naegele's rule: EDD = LMP + 280 days (40 weeks). Each step in the calculation is shown so you can verify the result manually.