What fetal weight percentile means
During pregnancy, an ultrasound can produce an estimated fetal weight (EFW) based on measurements of the head, abdomen, and thigh bone. Comparing that estimate to a reference curve for the same gestational age gives a percentile, showing whether growth is tracking near the middle of the expected range, or toward the higher or lower end.
How this calculator works
Enter the gestational age in weeks and the estimated fetal weight from your ultrasound report. The calculator compares your EFW to typical median fetal weight values for that gestational age (based on commonly used fetal growth reference curves such as Hadlock) and estimates a percentile using a standard statistical approximation.
Note: Estimated fetal weight itself carries a margin of error, and different ultrasound machines or reference charts can produce slightly different percentiles. This tool is for general educational purposes only — always rely on your obstetric provider’s interpretation of your specific ultrasound results.