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HealthType your height into any "ideal weight calculator" and it spits out a single confident number — 68 kg, 72.5 kg, 154 lb. It looks like science. But where do these numbers come from, and should you believe them? The honest answer is more interesting than the formulas.
This guide walks through the four classic formulas, their real origins, and the one method that actually holds up.
Try it yourself: Compare all four formulas for your height in one click. Ideal Weight Calculator →
The four classic formulas
All of them are linear: a base weight at 5 feet (152.4 cm), plus a fixed amount per inch above it.
| Formula | Men | Women |
|---|---|---|
| Devine (1974) | 50 + 2.3 × in over 5 ft | 45.5 + 2.3 × in over 5 ft |
| Robinson (1983) | 52 + 1.9 × in over 5 ft | 49 + 1.7 × in over 5 ft |
| Miller (1983) | 56.2 + 1.41 × in over 5 ft | 53.1 + 1.36 × in over 5 ft |
| Hamwi (1964) | 48 + 2.7 × in over 5 ft | 45.5 + 2.2 × in over 5 ft |
Results are in kilograms. For a 5'10" (70-inch) man: Devine gives 50 + 23 = 73 kg, Robinson gives 52 + 19 = 71 kg, Miller gives 56.2 + 14.1 = 70.3 kg, Hamwi gives 48 + 27 = 75 kg. Four formulas, four different "ideals" — the disagreement is the message.
What the formulas were actually for
- Devine (1974): created to estimate drug dosages — dosing by "ideal" body weight avoids overdosing obese patients. It was never a fitness target.
- Hamwi (1964): built for diabetic medication dosing — again, a clinical tool.
- Robinson and Miller (1983): attempts to improve on Devine using different population data — still population-level approximations.
None of them accounts for frame size, muscle mass, age, or body composition. A 5'10" athlete at 85 kg of muscle and a 5'10" sedentary person at 85 kg get the same "ideal" — which tells you everything about the formulas' limits.
The honest answer: a range, not a number
The most defensible approach is the BMI-range method: your healthy weight range is whatever keeps your BMI between 18.5 and 24.9:
Healthy range = 18.5 × height² (m) to 24.9 × height² (m)
For our 5'10" (1.78 m) man: 18.5 × 3.17 = 58.6 kg to 24.9 × 3.17 = 78.9 kg. That's a 20 kg-wide range — and that's the point. It's honest about uncertainty, and it's tied to population health data rather than a 1970s dosing shortcut.
But even the range is just a screening band. For a personal target, body fat percentage, waist circumference, and how you actually feel and function beat every formula.
Using "ideal weight" numbers sensibly
- As a sanity check: if you're far outside every formula's range, it's a prompt to look closer — not a verdict.
- Never as a deadline: the number wasn't designed for your body, so hitting it exactly proves nothing.
- Watch the direction, not the destination: consistent movement toward the healthy range, confirmed by body fat % and measurements, matters more than any single weigh-in.
Frequently asked questions
None of them is truly accurate — they were designed for drug dosing and life-insurance tables, not personal targets. The BMI-range method (18.5–24.9 × height²) is the most defensible because it gives a range tied to population health data rather than a single invented number.
For men: 50 kg + 2.3 kg for every inch over 5 feet. For women: 45.5 kg + 2.3 kg for every inch over 5 feet. A 5'10" man: 50 + 2.3 × 10 = 73 kg. Devine created it in 1974 to estimate drug dosages, not fitness targets.
Treat it as a rough reference point, not a goal. Muscle mass, frame size, age, and body composition shift what is healthy for you. Body fat percentage, waist measurement, and how you feel and function are better targets than any single number.
Because the formulas were built from different data for different purposes — drug dosing, insurance tables, or simple height scaling. They typically disagree by 5–10 kg, which itself proves no single number is "ideal."
Disclaimer: Calculator health content is for education only — not medical advice. Body metrics are screening tools, not diagnoses. If you have concerns about your health, speak with a qualified health professional.