The Hamwi IBW formula
The Hamwi formula, originally developed in 1964, remains widely used in clinical practice for its simplicity. For men: 48 kg for the first 5 feet of height, plus 2.7 kg for each inch over 5 feet. For women: 45.5 kg for the first 5 feet, plus 2.2 kg for each inch over 5 feet. The formula predicts IBW as a function of height only, without adjusting for age or body frame, making it a broad population-level estimate rather than an individualised ideal weight.
Multiple IBW formulas exist — Hamwi, Robinson, Devine, and Miller — and produce slightly different results. The Hamwi formula is most commonly used in dietetics and drug dosing contexts in the UK and US. The 0.4 correction factor in the AdjBW formula is based on the empirical observation that roughly 40% of excess body weight in obese patients consists of lean tissue (metabolically active mass), though this varies considerably with degree of obesity.