These formulas were not built for this
The Devine formula was published in 1974 to calculate drug dosages, not to prescribe body weight. Robinson, Miller and Hamwi followed with similar clinical aims. All four depend on height alone, ignoring frame size, muscle mass and body composition entirely.
They disagree with each other by several kilograms at the same height, which is itself informative: there is no single ideal weight, only a range compatible with good health.
Frame size and what the formulas ignore
None of these formulas account for build. A traditional adjustment measures wrist circumference relative to height to classify frame as small, medium or large, then shifts the target by roughly 10% in either direction. It is crude, but it acknowledges something the height-only formulas do not.
Muscle mass is the larger omission. A trained lifter can sit well above every formula's output while carrying less fat than someone at the "ideal" figure, which is why body composition is the more useful measure.
A range, not a target
The healthy BMI range spans roughly 6 to 8 kilograms at a typical adult height. That breadth is not imprecision — it reflects genuine variation in healthy body composition between people of the same height.
Health outcomes track behaviour more closely than they track weight. Someone active and eating well at the upper end of the range is generally better off than someone sedentary sitting at the formula's exact figure.
Frequently asked questions
Which formula should I trust? +
None over the others. Use the healthy BMI range as the practical target, and judge progress by strength, energy and blood markers rather than a specific number.
Why do the four formulas disagree? +
They were derived from different populations for different clinical purposes, mostly drug dosing rather than weight goals. The spread between them is a fair indication of how approximate any single figure is.
Do these apply to children? +
No. Children and teenagers are assessed against age and sex-specific growth percentiles, not adult formulas.