Where these formulas come from
In 1974 the pharmacist B. J. Devine proposed a simple rule for estimating lean body weight when dosing drugs: start with a base weight at 5 feet and add a fixed amount for every inch above it. It caught on far beyond pharmacy. Later researchers kept the same straight-line shape but refitted the numbers — J. D. Robinson and D. R. Miller in 1983, both against insurance-company height–weight tables — while G. J. Hamwi's 1964 version predates them all. None was derived from health outcomes, which is why the BMI range is shown alongside.
The formulas
h = inches over 5 feet result in kilograms Devine men 50 + 2.3 h women 45.5 + 2.3 h Robinson men 52 + 1.9 h women 49 + 1.7 h Miller men 56.2 + 1.41 h women 53.1 + 1.36 h Hamwi men 48 + 2.7 h women 45.5 + 2.2 h BMI range = 18.5 × m² to 24.9 × m² (m = height in meters)
Worked example
A man 5 ft 10 in tall is 10 inches over 5 feet. Devine: 50 + 2.3 × 10 = 73 kg (161 lb). Robinson: 52 + 19 = 71 kg (157 lb). Miller: 56.2 + 14.1 = 70.3 kg (155 lb). Hamwi: 48 + 27 = 75 kg (165 lb).
His height is 1.778 m, so the healthy BMI range is 18.5 × 3.161 = 58.5 kg to 24.9 × 3.161 = 78.7 kg — 129 to 174 lb.
A woman 5 ft 5 in tall (h = 5) gets 56.5–59.9 kg (125–132 lb) from the four formulas and a BMI range of 111–150 lb.
Limitations
- For adults only; children and teens need growth charts.
- The formulas ignore age, frame, muscle mass and ethnicity.
- They were never meant as weight-loss targets; a weight anywhere in the healthy BMI range can be fine.
Sources: Devine BJ, "Gentamicin therapy," Drug Intell Clin Pharm 1974;8:650–655; Robinson JD et al., Am J Hosp Pharm 1983;40:1016–1019; Miller DR et al., Am J Hosp Pharm 1983;40:1622; Hamwi GJ, in Diabetes Mellitus: Diagnosis and Treatment, American Diabetes Association, 1964; Pai MP & Paloucek FP, "The origin of the 'ideal' body weight equations," Ann Pharmacother 2000;34:1066–1069; CDC, Adult BMI Categories.
Frequently asked questions
Why do the four formulas give different answers?
They were fitted to different data for different purposes. Devine (1974) was written to dose medicines; Robinson and Miller (both 1983) re-fitted it to the 1959 and 1983 Metropolitan Life insurance tables; Hamwi (1964) is a clinical rule of thumb. For a 5 ft 10 in man they range from 70 to 75 kg (155 to 165 lb) — treat that spread as the honest uncertainty.
Is ideal body weight the same as a healthy weight?
Not exactly. "Ideal body weight" formulas give one number per height and sex, mainly used for medication dosing and ventilator settings. The CDC healthy BMI range (18.5 to 24.9) gives a band, which is a better guide for most adults. The calculator shows both.
Does frame size or muscle matter?
Yes. None of the formulas know your muscle mass or frame. Hamwi's original method suggested adding or subtracting 10% for a large or small frame. A muscular person can be well above every formula and very healthy.
What if I am shorter than 5 feet?
The formulas were built for adults 5 ft and taller. Below that, the calculator extends the same line downward, which some clinicians do (subtracting the per-inch amount), but the results are less reliable — rely on the BMI range instead.
This calculator is for general information and screening only and is not medical advice. Talk to a doctor or registered dietitian before making changes based on the result, especially if you are pregnant, under 18, or managing a health condition.