Pregnancy Week Calculator
Calculate how many weeks pregnant you are from your last menstrual period (LMP) or conception date. See your trimester and estimated due date.
Pregnancy is typically 40 weeks, calculated from the first day of your last menstrual period (LMP) — even though conception usually occurs 2 weeks later. This calculator tells you your exact week, trimester, and estimated due date.
Pregnancy trimesters
- First trimester (weeks 1–12): major organ formation, highest miscarriage risk, morning sickness common
- Second trimester (weeks 13–26): baby movement begins, energy often improves, anatomy scan around week 20
- Third trimester (weeks 27–40): rapid weight gain, baby positions for birth, increasing discomfort
Important prenatal milestones
- Week 8–10: first ultrasound, heartbeat confirmed
- Week 10–13: NIPT (non-invasive prenatal testing) / CVS optional
- Week 16–20: amniocentesis if indicated
- Week 20: anatomy scan (mid-pregnancy ultrasound)
- Week 24: glucose screening for gestational diabetes
- Week 36+: weekly OB visits