Due Date Calculator
Calculate your expected baby due date based on LMP, conception, or ultrasound.
Due Date Calculator
Calculate your expected baby due date based on LMP, conception, or ultrasound.
How is the Due Date Calculated?
Most pregnancies last around 40 weeks (280 days) from the first day of your last menstrual period (LMP). Our calculator uses Naegele's rule for LMP calculations and adjusted timelines for conception and ultrasound data to give you the most accurate estimate possible.
Naegele's Rule
The standard way to calculate a due date is by using Naegele's rule, named after the German obstetrician Franz Karl Naegele. It involves adding seven days to the first day of your last menstrual period (LMP) and then subtracting three months.
Ultrasound Dating
In the first trimester, an ultrasound is often the most accurate way to date a pregnancy. It measures the crown-rump length (CRL) of the embryo to determine its gestational age.