Ideal Weight Calculator

These formulas were built for drug dosing, not for goals

The Devine formula appeared in 1974 in a paper about gentamicin dosing. Hamwi's came from a 1964 diabetes guide. Robinson and Miller both published revised versions in 1983 after comparing the originals against population data. None of them was validated as a health target, and none of them considers age, frame size, muscle mass or ethnicity — only height and sex.

They survive because a single number is convenient in a hospital. They spread into fitness culture because a single number is also convenient for selling things. Treat the spread between the four as what it is: evidence that no single “ideal” weight exists.

What the healthy BMI range actually says

Public health guidance uses a range, not a point: BMI 18.5 to 24.9 for adults. At 178 cm that is roughly 58.6 kg to 78.9 kg — a span of over 20 kg, all of it considered healthy. That width is deliberate. It reflects genuine variation in build between people of the same height, which a formula returning one number cannot express.

Where BMI stops being useful

BMI is a ratio of mass to height squared. It cannot tell muscle from fat, so it misclassifies very muscular people as overweight and can miss excess fat in people with little muscle. It was never designed for individuals — Quetelet devised it in the 1830s to describe populations. For an individual, waist measurement and body composition tell you more, and a clinician who can see you tells you more still.

Frequently Asked Questions