Calculate your pregnancy due date from your last menstrual period (LMP).
The Pregnancy Due Date Calculator estimates your baby's due date using Naegele's rule — the standard obstetric method. Enter the first day of your last menstrual period (LMP) and the calculator adds 280 days (40 weeks) to estimate your due date. You will also see how many weeks pregnant you currently are and how many days remain. This is the same method used by doctors at the first prenatal visit.
1. Enter the year, month, and day of your last menstrual period (LMP).
2. The calculator adds 280 days to estimate your due date.
3. See the due date, current gestational age in weeks, and days remaining.
Naegele's Rule:
Due Date = LMP Date + 280 days (40 weeks)
Gestational Age (weeks) = (Today - LMP Date) / 7
Days Remaining = Due Date - Today
Example: LMP = January 1, 2026
Due Date = January 1 + 280 days = October 8, 2026
If today is March 29, 2026:
Weeks pregnant = (Mar 29 - Jan 1) / 7 = 87 / 7 = 12 weeks
Days remaining = Oct 8 - Mar 29 = 193 days