Why “ideal weight” is a range, not a number
Each of these formulas was created decades ago for a specific clinical use case — Devine (1974) for medication dosing, Hamwi (1964) for diabetes nutrition counselling, Robinson (1983) and Miller (1983) as refinements for taller patients, Peterson (2016) as a modern BMI-anchored replacement. None were designed as universal “you should weigh exactly this” predictors. For most healthy adults, any weight in the BMI 20–25 range is metabolically equivalent.
Better targets than scale weight
- Waist circumference: <94 cm men, <80 cm women
- Waist-to-height ratio: <0.5 — “keep your waist less than half your height”
- Body fat %: see our Body Fat Calculator
- Strength markers: carry your bodyweight comfortably; deadlift at least 1× your bodyweight; walk 10,000 steps without fatigue
- Metabolic markers: fasting glucose, lipid panel, blood pressure — these don't care about your weight if they're normal
What the formulas actually do
They all start with a baseline weight at 5 feet of height, then add a fixed weight per inch above 5 feet. The differences are in those two numbers. Devine and Hamwi are the steepest; Miller and Peterson are gentler at tall heights. Robinson sits in between. In practice they agree to within 5 kg for average heights and diverge more at the extremes.
When “ideal” stops meaning healthy
Older adults (70+) actually live longest at BMI 25–30, not the “healthy” 18.5–24.9 — a phenomenon called the obesity paradox. A bit of reserve weight protects against falls, hospitalization, and frailty. Athletes may carry significantly above the BMI range and be metabolically perfect. Pregnant and lactating women have entirely different targets. The formulas are starting points for conversations, not finish lines.