Updated June 17, 2026
Find your due date
Get your estimated due date and current week in seconds.
You count pregnancy weeks from the first day of your last menstrual period (LMP), not from conception. If your LMP was 10 weeks ago today, you are currently 10 weeks pregnant, even though the embryo is only about 8 weeks old. This LMP-based system is used universally because the exact date of conception is often unknown, while most people can recall when their last period started.
How to calculate your current week
Count the number of complete weeks between the first day of your LMP and today. If it has been 63 days since your LMP, divide by 7 to get 9 weeks. The Due Date Calculator does this automatically and also shows your current trimester. If you do not remember your LMP, an early ultrasound can estimate your gestational age from the size of the embryo or fetus.
Weeks vs months: why it can feel confusing
Pregnancy is 40 weeks, which is about 10 months by the calendar, not 9. The "9 months" phrasing comes from counting lunar months (4 weeks each) or simply from rounding. Clinicians always work in weeks because it is more precise. Saying "I'm 28 weeks" tells a provider much more than "I'm 7 months."
What does each week mean?
Each week represents a distinct stage of fetal development. The first few weeks involve implantation and very early cell division. By week 6 a heartbeat is often detectable. Week 20 is roughly the midpoint. Weeks 24 to 28 mark the threshold of viability outside the womb with intensive care. Weeks 37 to 42 are the full-term range. See the trimester breakdown for a full week-by-week overview.
Gestational age vs fetal age
Gestational age is counted from LMP and is what doctors use. Fetal age (also called embryonic age) is counted from conception and runs about 2 weeks behind. If your provider says you are 20 weeks pregnant (gestational), the fetus is about 18 weeks old. Unless specified otherwise, any week reference in medical contexts uses gestational age.
Always confirm your dates and any questions about your pregnancy with your doctor or midwife. An ultrasound dating scan in the first trimester is the clinical standard.
Find your due date
Get your estimated due date and current week in seconds.