Ideal Body Weight Calculator Guide: What the Formulas Actually Measure
Where the Devine, Robinson, Miller, and Hamwi ideal body weight formulas came from, why they were designed for medical dosing, and how to interpret the range.
"Ideal body weight" sounds like a fitness or cosmetic target, but the formulas behind it were actually developed for a much more clinical purpose — estimating a reference weight for calculating medication dosages.
Where these formulas come from
- Devine (1974): the most widely used in clinical practice today, still referenced for drug dosing calculations.
- Robinson (1983) and Miller (1983): later refinements with slightly different coefficients based on their own study populations.
- Hamwi (1964): the oldest of the four, originally popularized as a quick clinical rule of thumb.
Why the range matters more than any single number
Because these four formulas were derived independently, they don't perfectly agree — and that's expected, not a flaw. Showing the full range from the Ideal Body Weight Calculator alongside the average is more honest than presenting one formula's output as a definitive target.
What frame size adjusts for
People of the same height can have meaningfully different bone structure, which is what the small/medium/large frame adjustment roughly accounts for — a rough approximation, not a precise measurement, since true frame size is sometimes assessed clinically using wrist circumference relative to height.