Naegele's Rule for Pregnancy - Due Date Calculator
Naegele's rule (Nagel's rule) predicts an estimated due date based on the woman's last menstrual period. This page only provides an estimate for the due date, and does not take into account small changes such as leap years. It also does not take into affect months with less than 31 days.
Due Date = LMP + 9 months + 7 days
Enter the digits for LMP, 2 digits for month and date and four digits for the year.
The official tool used by physicians to estimate gestational age from a due date confirmed by ultrasound is the Pregnancy Wheel and Ovulation Calendar.
1. Le, Tao, and Vikas Bhushan. First Aid for the USMLE Step 2 CK. 5th ed. New York: McGraw-Hill, 2006.