Ideal Weight Calculator

Not from health research. Devine’s equation appeared in a 1974 pharmacy note as a convenient way to estimate doses of gentamicin, and it remains in drug references for exactly that. Hamwi’s came from 1964 diabetic diet work; Robinson’s and Miller’s are 1983 refits against insurance-company height–weight tables. None was tested against mortality, illness or fitness, which is why "ideal" is doing a lot of work in the name.

Because each fitted a different sample with a different slope. They all take a base weight at 5 feet and add a fixed amount per inch — Hamwi adds 2.7 kg per inch for men, Miller only 1.41 — so they separate as height rises. At 6 feet the four can be 10 kg apart for the same man. Four confident, incompatible answers to the same question is a reason to treat all of them as rough.

A range rather than a number. The BMI 18.5–24.9 band at your height is the usual answer, and it is deliberately wide — about 14 kg or 30 lb for a typical adult — because that is what the outcome data supports. Where you sit inside it depends on build, muscle and history. Waist circumference adds information BMI misses: over 94 cm (37 in) for men or 80 cm (31.5 in) for women marks raised risk regardless of BMI.

For this question, yes — it gives a range from population outcome data rather than a point from a dosing rule. But it has its own limits: it cannot tell muscle from fat, so it misclassifies muscular people as overweight, and it reads differently across ethnic groups. WHO and several national bodies apply lower thresholds for South Asian and East Asian populations, where cardiometabolic risk rises at a lower BMI.

A rough classification of skeletal build, usually from wrist circumference relative to height. Only the Hamwi formula uses it, adjusting by ±10%. It is a crude proxy — bone mass varies less between adults than the ±10% implies — and it cannot rescue a formula that was not measuring health in the first place. Treat it as a footnote, not a correction.

Somewhere in a range, not at a single number. An IBW calculator using the Devine formula gives about 66 kg for a 170 cm man and 61.5 kg for a woman of the same height, but those formulas were built for drug dosing, not health, and the four classic ones disagree by several kilograms at any height. The evidence-based answer to how much you should weigh is the BMI 18.5 to 24.9 band, which at 170 cm runs from 53.5 to 72 kg. This page shows the formula values and that range side by side so you can see how far apart they are.

The most used ideal body weight formula is Devine (1974): 50 kg plus 2.3 kg for every inch over five feet for men, 45.5 kg plus 2.3 kg per inch for women. A Devine formula calculator is what hospital dosing tools run, which is the only setting the formula was designed for. An ideal weight chart lays the same formulas out by height, and reading one shows the problem: at every height the four classic formulas disagree by several kilograms, and none matches the ideal weight for height that health data supports, which is a range. This page gives the formula values and the range together so you can see both.