Pregnancy Week Calculator
Find out how far along you are in your pregnancy. Enter your last period date to see your current week, trimester, due date, and baby size. Completely private — runs in your browser.
How the Pregnancy Week Calculator Works
Pregnancy is counted from the first day of your last menstrual period (LMP), not from conception. A full-term pregnancy is 40 weeks (280 days). This pregnancy week calculator determines your current week, trimester, estimated due date, and shows baby development milestones for your stage.
Pregnancy Timeline
1st Trimester: Weeks 1-12 (development begins)
2nd Trimester: Weeks 13-26 (quickening, growth)
3rd Trimester: Weeks 27-40 (final development)
Due Date = LMP + 280 days (Naegele's Rule)
Understanding Pregnancy Weeks
Pregnancy weeks can be confusing because counting starts from your last period, about 2 weeks before conception. So when you are "4 weeks pregnant," the embryo is actually about 2 weeks old. This standard counting method (gestational age) is used by doctors worldwide.
Baby Development by Trimester
In the first trimester, all major organs begin forming. The heart starts beating around week 6. By the second trimester, the baby can move, hear sounds, and you may feel kicks. The third trimester is about growth and lung development. By week 37, the baby is considered full-term.