Gestational Age Calculator

About this calculator

Gestational age is the standard way pregnancy duration is measured in obstetrics, counted in completed weeks and days from the first day of the last menstrual period (LMP) rather than from the estimated date of conception, which typically falls about two weeks later. A full-term pregnancy runs roughly 40 weeks (280 days) from LMP, and this convention is used consistently across prenatal visits, ultrasound dating and due-date calculations even though actual ovulation and fertilization occur later in the cycle.

Obstetricians, midwives and pregnant people use gestational age to track fetal development milestones, schedule prenatal screenings and tests that are only meaningful within specific week windows, and determine the estimated due date, with early ultrasound measurements sometimes used to adjust the LMP-based estimate if cycle length was irregular.

This calculator takes the number of days since your last menstrual period and returns your current gestational age in completed weeks and days.