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Gestational Age Calculator

Calculates current gestational age from the last menstrual period.

When to use: Determines gestational age in weeks and days to guide management decisions — antenatal investigations, viability assessment, timing of interventions, and appropriate fetal growth benchmarking.
Calculator
Enter number of days since LMP started

Fill in all fields to see the result

Formula
Gestational Age = Days since LMP ÷ 7 Expressed as weeks + days (e.g., 28+3)
Key Points for NEET PG
  • GA = days since LMP / 7; normal term delivery at 37–42 weeks (40 weeks = EDD)
  • Viability threshold: 22–24 weeks in most centres; survival >50% from 25 weeks
  • Screening timing: NT scan 11–13+6 weeks; anomaly scan 18–20 weeks; GDM screen 24–28 weeks
  • Preterm: <37 weeks; Late preterm: 34–36+6; Early term: 37–38+6; Full term: 39–40+6; Late term: 41
  • Dating discrepancy >7 days in first trimester or >14 days in second: adjust EDD to ultrasound
References
ACOG Practice Bulletin: Medically Indicated Late-Preterm and Early-Term Deliveries · Obstetrics & Gynecology (2019)
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