Calculator
Pregnancy Week Calculator
Find out exactly how many weeks and days pregnant you are today. Enter the first day of your last period — or, if you already know it, your due date.
Enter a date above to calculate how many weeks pregnant you are.
Understanding gestational age
In obstetrics, pregnancy is measured in weeks + days from the first day of your last menstrual period (LMP), not from conception. So on the day your period started you were “0 weeks 0 days,” and at 40w0d you've reached your estimated due date.
Trimesters are a convenient shorthand for the three phases of pregnancy: the first trimester runs from week 0 through week 12, the second trimester from week 13 through week 26, and the third trimester from week 27 until birth.