Devine, Robinson, Miller and Hamwi formulas plus the healthy BMI range.
“Ideal” weight from height-only formulas was originally devised for medication dosing, not body composition. Use it as a ballpark; muscle mass, frame size, and body-fat distribution are not captured.
"Ideal body weight" (IBW) is a long-running medical concept, originally devised in the mid-twentieth century not for body-image purposes but for drug dosing. Many medications dose by weight, but for very tall or very short patients the dose-response curve is non-linear with body mass; clinicians normalize to an idealized weight tied to height. Four formulas dominate the literature: Devine (1974), the dosing standard; Robinson (1983) and Miller (1983), two refinements; and Hamwi (1964), the older grandparent still used in dietetics. They all share the same shape — a base weight at 5 ft (152.4 cm) plus a per-inch increment over 5 ft, sex-adjusted. They diverge in the slope and the base, so for the same height they spread by 5–10 kg. The calculator runs all four, reports the average as the headline number, and overlays the WHO healthy-BMI weight range for context.
Heights converted to inches (h_in). Inches over 5 ft: x = max(0, h_in − 60). Then for each formula, with male/female bases: - Devine: 50 (M) / 45.5 (F) + 2.3 · x - Robinson: 52 (M) / 49 (F) + 1.9 · x - Miller: 56.2 (M) / 53.1 (F) + 1.41 · x - Hamwi: 48 (M) / 45.5 (F) + 2.7 (M) / 2.2 (F) · x
All in kilograms. Average of the four = the headline. Healthy BMI weight range: BMI 18.5–25 × height² (m²). The calc converts the final result to kg or lb based on the user's preference.
Pick sex (the formulas are sex-stratified — drug dosing convention; not a body-image judgment). Enter height in cm, m, or ft+in (the unit selector keeps values synchronized when you switch). Pick the output unit for the result. The headline KPI is the four-formula average; below it, the WHO healthy-BMI range; on the right, the four individual formula outputs side by side.
Man, 175 cm = 68.9 in, x = 8.9 in over 5 ft. - Devine: 50 + 2.3 × 8.9 = 70.5 kg - Robinson: 52 + 1.9 × 8.9 = 68.9 kg - Miller: 56.2 + 1.41 × 8.9 = 68.8 kg - Hamwi: 48 + 2.7 × 8.9 = 72.0 kg - Average: 70.0 kg. - Healthy BMI range at 1.75 m: 18.5 × 3.0625 = 56.7 kg → 25 × 3.0625 = 76.6 kg → 56.7 – 76.6 kg.
The four-formula average sits comfortably inside the healthy BMI band, which is the usual sanity check.
Height-only formulas miss frame size. A 175-cm man with broad shoulders and dense bones has a higher healthy weight than a 175-cm man with a small frame, and the IBW formulas can't tell. Combine with body-fat percentage (Navy circumference method or DEXA) for a real composition picture.
Muscle mass. Athletes with high muscle mass routinely sit above the four-formula average — and above the healthy BMI cap. They are not unhealthy; the formula is just bad at distinguishing muscle from fat. Pair this calc with a body-fat measurement.
Sex assigned at birth, not gender identity. The slope and base values were derived from sex-disaggregated population data. The calculator uses "male" / "female" as proxies for the biology underlying the formula, not as identity labels. Use the option that matches the body composition pattern you most identify with.
Pediatric, pregnant, post-bariatric. The IBW formulas were derived for non-pregnant, non-pediatric adults. Pediatric dosing uses growth charts; pregnancy uses pre-pregnancy IBW with a trimester-specific gain target; post-bariatric patients have rapidly-changing lean mass that breaks the assumption.
Disagreement among formulas. Hamwi tends to run high, Miller low, Devine and Robinson in the middle. The 5-kg spread is real biological variability, not a calculator error. Use the average as a single number, the spread as a confidence interval.
"Ideal" is a clinical term, not a target. The original purpose was drug dosing, not body-image. Some patients use IBW as a goal weight — that's fine if your physician concurs, but the formulas were not designed for cosmetic targeting and don't pretend to capture the full picture of metabolic health.