Everyday
Pregnancy Due Date Calculator
Find out your baby's estimated due date.
How Due Dates Are Calculated
A full-term pregnancy lasts approximately 40 weeks (280 days) from the first day of the last menstrual period (LMP). Naegele's Rule is the standard method: add 1 year, subtract 3 months, add 7 days to the LMP date.
Pregnancy Trimester Breakdown
- First trimester: Weeks 1–12 — major organ development; morning sickness common
- Second trimester: Weeks 13–26 — energy returns; anatomy scan typically at week 20
- Third trimester: Weeks 27–40 — rapid fetal growth; birth preparation
Key Prenatal Milestones
- Week 12: first trimester screening (nuchal translucency ultrasound)
- Week 20: anatomy scan — most detailed ultrasound; can determine sex
- Week 24: viability threshold — survival outside womb becomes possible
- Week 37: "early term"; week 39–40 = full term
This tool provides estimates only. Your healthcare provider will confirm your due date via ultrasound.
How accurate is a due date calculation?
Only about 4% of babies are born exactly on their due date. Most births occur within 2 weeks before or after the estimated date. First trimester ultrasound (8–14 weeks) is the most accurate dating method, with a margin of ±5–7 days. The due date is best viewed as a "due month" rather than a specific day.
What is gestational age vs fetal age?
Gestational age (GA) counts from the first day of the last menstrual period — this is what your OB/GYN uses. Fetal age counts from actual conception, typically about 2 weeks after LMP. This means at "6 weeks pregnant" (gestational), the embryo is actually about 4 weeks old. All standard pregnancy calendars use gestational age.