Pregnancy Week Calculator: How Many Weeks Pregnant Are You?
Knowing your exact gestational age matters for prenatal care scheduling, understanding your baby's development stage, and timing your screenings correctly. This calculator gives you your current pregnancy week and trimester from just one date.
How Gestational Age Is Counted
Pregnancy is counted from the first day of your last menstrual period (LMP) — not from the date of conception. This means gestational age includes approximately 2 weeks before conception actually occurred. A full-term pregnancy is 40 weeks (280 days) from LMP.
This convention is used because LMP is a known, recorded date while the exact date of conception is rarely certain.
Trimester Breakdown
| Trimester | Weeks | Key Developments |
|---|
| First | 1–13 | All major organs form; heart begins beating (~week 6) |
| Second | 14–26 | Baby moves (quickening); anatomy scan; gender visible |
| Third | 27–40 | Rapid growth; lung maturation; birth preparation |
Find your exact week with our Pregnancy Week Calculator.
Week-by-Week Milestones
- Week 6: Heartbeat detectable by ultrasound
- Week 12: End of first trimester; miscarriage risk drops significantly
- Week 18–20: Anatomy scan — checks organ development and can reveal gender
- Week 24: Age of viability — survival possible with intensive care
- Week 28: Third trimester begins; growth charts become more significant
- Week 36: Baby is considered late preterm; hospital bag should be ready
- Week 37: Full term — can safely deliver any time from here
- Week 40: Estimated due date
Screening and Appointment Schedule
Weeks 8–12: First prenatal appointment, dating scan, blood tests (blood type, anemia, infections).
Week 12–13: First trimester combined screening (nuchal translucency + blood tests).
Week 18–20: Detailed anatomy ultrasound.
Week 28: Glucose tolerance test for gestational diabetes; Rh antibody check.
Week 35–36: Group B Streptococcus swab.
Practical Tips
Keep a pregnancy journal by week. Recording symptoms, appointments, and milestones creates a meaningful record for both practical and sentimental reasons.
Prepare birth plan from week 28. Thinking through preferences for labour and delivery before the third trimester gives you time to discuss options with your care team.
Final Thoughts
Knowing your exact pregnancy week helps you understand your baby's development, schedule your prenatal care correctly, and feel connected to each stage of your pregnancy.
Find your current week and trimester with our free Pregnancy Week Calculator.