Estimated Birth Weight Calculator

The Estimated Birth Weight Calculator estimates fetal weight in grams using ultrasound measurements like BPD and AC alongside maternal stats. This tool helps expectant parents and healthcare providers assess fetal growth before delivery. Whether you are planning for birth, checking for macrosomia, or tracking development, this calculator offers reliable projections based on established medical data.

Weeks of pregnancy (between 20-42 weeks)
Height in centimeters
Pre-pregnancy weight in kilograms
Age in years
Number of previous births (not including current pregnancy)
Ultrasound measurement in centimeters
Ultrasound measurement in centimeters

How Estimated Birth Weight Is Calculated

Estimated birth weight predicts the fetus's mass near delivery. It uses a regression equation combining ultrasound biometry with maternal demographics to approximate size accurately.

(Gestational Age × 95) + (BPD × 135) + (AC × 45) + (Maternal Height × 8.5) + (Maternal Weight × 12) + (Parity × 25) + (Sex × 60) - 4230

Where:

  • Gestational Age = Weeks of pregnancy
  • BPD = Biparietal Diameter (cm)
  • AC = Abdominal Circumference (cm)
  • Parity = Number of previous births
  1. Measure fetal dimensions like head diameter and abdomen size via ultrasound to assess physical growth.
  2. Input maternal factors such as height, weight, and parity to account for genetic influences.
  3. Apply specific weighted coefficients to each input to calculate the final total in grams.

What Your Estimated Birth Weight Means

This number indicates your baby's projected size at birth, helping you and your doctor prepare for the safest delivery plan.

Low Birth Weight (< 2,500 g): Estimates below 2,500 grams suggest a smaller baby. This may prompt your doctor to monitor for growth restrictions or plan for potential NICU support.

Normal Birth Weight (2,500 – 4,000 g): Falling in this range generally indicates the baby is growing well. Most vaginal deliveries occur safely within this weight category without specific size-related interventions.

Macrosomia (> 4,000 g): A result above 4,000 grams suggests a larger baby. In this scenario, your provider might discuss the risks of shoulder dystocia or the possibility of a cesarean section.

Important: These are statistical estimates, and actual birth weight can vary by 10-15%.

This tool is for informational purposes only and is not a substitute for professional medical advice. Always consult your obstetrician or healthcare provider regarding your specific medical condition and delivery options. Remember that conditions like gestational diabetes can also influence final weight.

Use this result alongside fundal height measurements and third-trimester ultrasounds for a complete picture of fetal health.

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