Fetal Weight Calculator

Your scan report lists the measurements in mm or cm. Enter them as shown and choose the unit.

How it is calculated

The Hadlock (1985) four-parameter formula, in centimetres:

log10(EFW) = 1.3596 − 0.00386·AC·FL + 0.0064·HC + 0.00061·BPD·AC + 0.0424·AC + 0.174·FL

Without BPD, the three-parameter version is used:

log10(EFW) = 1.326 − 0.00326·AC·FL + 0.0107·HC + 0.0438·AC + 0.158·FL

The result is in grams, with a typical error of ±10–15%.

Around 32 weeks: BPD 8.2, HC 29.5, AC 28, FL 6.2 cm: estimated weight ≈ 1,925 g.

How accurate is ultrasound weight?

Typically within 10–15% either way, less accurate for very large or very small babies.

What do the abbreviations mean?

BPD head diameter, HC head circumference, AC abdominal circumference, FL femur length.

Is the weight normal for the gestational age?

Your doctor compares it with growth charts (percentiles); that needs a medical assessment.