Four formulas, one shared shape
Every ideal-body-weight formula does the same thing: start from a base weight for a 5-foot frame, then add a fixed amount for each inch above 60 inches. They differ only in the base and the per-inch step, and men get a higher base than women.
The four formulas (result in kg)
| Formula | Men | Women |
|---|---|---|
| Devine (1974) | 50.0 + 2.3 × (in − 60) | 45.5 + 2.3 × (in − 60) |
| Robinson (1983) | 52.0 + 1.9 × (in − 60) | 49.0 + 1.7 × (in − 60) |
| Miller (1983) | 56.2 + 1.41 × (in − 60) | 53.1 + 1.36 × (in − 60) |
| Hamwi (1964) | 48.0 + 2.7 × (in − 60) | 45.5 + 2.2 × (in − 60) |
To convert kg to pounds, multiply by 2.205. Devine is the default in clinical drug dosing; the others shift the estimate by a few kilograms in either direction.
Two adjustments that matter
- Frame size. A small frame trims the estimate by about 10%, a large frame adds about 10%. Wrist circumference is the most reliable way to judge it, so two people of the same height can differ by 9–14 kg and both be healthy.
- The BMI cross-check. A healthy weight also falls in the BMI 18.5–24.9 range. Because BMI scales with height squared, that range widens into a band of pounds, not a single figure — ideal weight sits inside it.
What the number leaves out
These formulas use only height, sex and frame. They cannot tell muscle from fat, so an athlete reads high, and they do not account for age or ethnicity, since they were built on older Western insurance data. In the clinic they are used for medication dosing and ventilator settings, where a repeatable estimate matters more than a perfect one.
Common questions
Which ideal-weight formula should I use?
Devine (1974) is the clinical standard, mostly because it is used for drug dosing. Robinson and Miller (both 1983) are more modern updates, and Hamwi (1964) is common in diet planning. They land within a few pounds of each other, so averaging all four is a fair approach.
How do the formulas actually work?
Each starts from a base weight at 5 feet (60 inches) and adds a fixed amount for every inch above that. Devine adds 2.3 kg per inch, Robinson about 1.9 for men and 1.7 for women. Men get a higher base weight than women.
Is ideal weight the same as healthy weight?
Not quite. Ideal body weight is an estimate from height alone, while a healthy weight also depends on body composition, age and fitness. A muscular person can sit above their ideal weight and still be healthy, so treat the number as a reference point, not a target.
