Gestational Age Calculator
Calculate gestational age from your last menstrual period.
See current week, trimester, and expected milestones.
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Gestational Age
Gestational age is the number of weeks since the first day of your last menstrual period (LMP).
Gestational Age = Today - LMP Date
Pregnancy milestones by gestational age:
- Week 4: Implantation occurs
- Week 6: Heartbeat may be detectable
- Week 8: Major organs begin forming
- Week 12: End of first trimester, risk of miscarriage drops
- Week 16: Gender may be visible on ultrasound
- Week 20: Anatomy scan, mother may feel movement
- Week 24: Viability milestone
- Week 28: Third trimester begins
- Week 37: Early term
- Week 39–40: Full term
- Week 42: Post-term
Trimester breakdown:
- First trimester: Weeks 1–12
- Second trimester: Weeks 13–27
- Third trimester: Weeks 28–40
Note: This is an estimate based on a 28-day cycle. An early ultrasound is the most accurate method for dating. Always consult your healthcare provider.