Pregnancy Due Date Calculator

About this calculator

This calculator estimates your due date using Naegele's rule adjusted for your cycle length. For a standard 28-day cycle, the due date is 280 days (40 weeks) from the first day of your last menstrual period (LMP). For longer or shorter cycles, the estimate shifts by the difference from 28 days — a 32-day cycle adds 4 days to the standard estimate. The result also shows your current gestational age, estimated conception date, current trimester, and key milestone dates throughout the pregnancy.

Field explanations

First day of last period

The date your most recent menstrual period began. Gestational age is counted from this date, even though conception typically occurs about two weeks later.

Average cycle length

The number of days from the start of one period to the start of the next. The standard assumption is 28 days. Valid range is 20–45 days. Longer cycles push the due date later; shorter cycles bring it earlier.