Ideal Weight Calculator

Ideal body weight formulas were originally developed for medication dosing in clinical settings, not for fitness or aesthetics. The Devine formula (1974) is the most-cited; Robinson, Miller, and Hamwi are variations on the same height-and-sex framework. None account for muscle mass, frame size, or body composition.

The calculator returns all four formulas for cross-reference. Treat the spread as a range, not a target.

Devine's 1974 formula was published in a letter to a pharmacy journal addressing gentamicin dosing. The formula — IBW (kg) = 50 + 2.3 kg per inch over 5 feet for men, 45.5 + 2.3 kg per inch over 5 feet for women — was a rough estimate for clinicians, not validated against population data. Robinson (1983), Miller (1983), and Hamwi (1964) followed the same height-based pattern with slightly different coefficients. None of these formulas account for body composition; a 6-foot man who weighs 88 kg might be lean and muscular at 12% body fat, or sedentary and overweight at 30% body fat — the IBW formulas can't tell the difference and predict the same "ideal" weight for both.

A worked example: a 5'10" (178 cm) male. Devine: 50 + (2.3 × 10) = 73 kg (161 lb). Robinson: 52 + (1.9 × 10) = 71 kg (157 lb). Miller: 56.2 + (1.41 × 10) = 70.3 kg (155 lb). Hamwi: 48 + (2.7 × 10) = 75 kg (165 lb). The four formulas give a range of 70.3 to 75 kg (155 to 165 lb) — about a 7% spread. A muscular athlete at this height could easily be 80–85 kg with low body fat and excellent metabolic health, well above any formula's "ideal." Conversely, someone at 70 kg who's sedentary with high body fat could be metabolically unhealthier than someone at 80 kg with appropriate muscle mass.

Limitations: these formulas are crude and outdated for any purpose other than rough medication dosing. For health and fitness goals, body fat percentage, waist-to-height ratio, and metabolic markers (blood pressure, lipids, fasting glucose) matter more than scale weight. The formulas predate modern understanding of body composition and were derived from limited population samples — primarily white American adults from mid-century data. Ethnic variation, athletic build, and frame size all sit outside their scope. Treat the calculator's output as a historical reference, not a personal target.