Pregnancy Due Date Calculator
Calculate your Estimated Due Date (EDD) using Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP).
For informational purposes only and does not constitute medical advice. Consult a professional healthcare provider for clinical pregnancy dating, which uses ultrasound measurement in the first trimester for the most accurate estimate.
About Naegele's Rule
Naegele's Rule, developed by German obstetrician Franz Karl Naegele in 1812, remains the standard method for estimating due date. It assumes a 28-day menstrual cycle with ovulation on day 14. The rule adds 280 days (40 weeks) to the LMP date. For cycles shorter or longer than 28 days, the estimated due date is adjusted accordingly. Only about 5% of babies are born on their exact due date; most arrive within two weeks before or after.