Calculators · Obstetrics & Gynaecology · Formula
Estimated fetal weight (Hadlock 1985)
Also called EFW, Hadlock IV, Hadlock formula, sonographic fetal weight
Ultrasound fetal weight from AC and FL, adding HC and/or BPD when available (Hadlock 1985 models; Hadlock IV when all four are entered).
Fill 2 more fields to see the result.
Formula and scoring
All in cm, EFW in g. Hadlock IV: log10 EFW = 1.3596 + 0.0064 HC + 0.0424 AC + 0.174 FL + 0.00061 BPD·AC − 0.00386 AC·FL. HC-AC-FL: 1.326 − 0.00326 AC·FL + 0.0107 HC + 0.0438 AC + 0.158 FL. BPD-AC-FL: 1.335 − 0.0034 AC·FL + 0.0316 BPD + 0.0457 AC + 0.1623 FL. AC-FL: 1.304 + 0.05281 AC + 0.1938 FL − 0.004 AC·FL.
Exam and ward pearls
- Models that include head, abdomen and femur are more accurate than head-and-abdomen models (Hadlock 1985).
When not to rely on it
- Accuracy falls at the extremes of weight (macrosomia, severe growth restriction), with oligohydramnios, obesity and late in the third trimester.
- Measurements must be entered in cm (or switch the unit to mm); entering mm as cm gives nonsense.
Source
- Hadlock FP, Harrist RB, Sharman RS, Deter RL, Park SK. Estimation of fetal weight with the use of head, body, and femur measurements—a prospective study. Am J Obstet Gynecol. 1985;151(3):333-7. doi:10.1016/0002-9378(85)90298-4 · PMID 3881966
- Warshafsky C, Ronzoni S, Quaglietta P, et al. Comparison of sonographic fetal weight estimation formulas in patients with preterm premature rupture of membranes. BMC Pregnancy Childbirth. 2021;21:149 (Table 2 lists the Hadlock 1985 coefficients). doi:10.1186/s12884-021-03631-w · PMID 33607956
Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.