Pregnancy Due Date Calculator
Estimate delivery dates using Naegele's rule (LMP + 280 days). Fast, free, and fully client-side.
Calculator Inputs
Last Menstrual Period (LMP)
Estimated Due Date—
Gestation Age—
How the Pregnancy Due Date Calculator Works
Estimates expected delivery date (EDD) and gestational age based on the first day of the last menstrual period (LMP) using Naegele rule.
Formula
Estimated Due Date = First Day of LMP + 280 Days (40 Weeks)
Naegele rule adds 1 year, subtracts 3 months, and adds 7 days to the first day of the last menstrual cycle.
Calculation Example
If your last menstrual period started on March 1, your estimated due date is December 6 (March 1 + 280 days).
Frequently Asked Questions
How accurate are due date calculations?
Only about 4% to 5% of babies are born on their exact estimated due date; most arrive within a two-week window before or after.