Life Calculator

Ideal Weight Calculator

There is no single ideal weight, and the four formulas below will give you four different answers. That disagreement is the most useful thing this page can show you.

Last reviewed: Written and checked by the Life Calculator editorial team
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All four formulas are driven almost entirely by height.

The four formulas

Every one of these shares a structure: a base weight at five feet, plus a fixed amount per additional inch. They differ only in the constants.

Devine (1974) Men 50.0 + 2.3 kg per inch over 5 ft Women 45.5 + 2.3 Robinson (1983) Men 52.0 + 1.9 kg per inch over 5 ft Women 49.0 + 1.7 Miller (1983) Men 56.2 + 1.41 kg per inch over 5 ft Women 53.1 + 1.36 Hamwi (1964) Men 48.0 + 2.7 kg per inch over 5 ft Women 45.5 + 2.2

Note the inch. All four were built in imperial units, which is why a metric height has to be converted first — and why none of them behaves sensibly below 152 cm, where the “inches over five feet” term goes negative.

Where they came from, and why it matters

These are not health targets. The Devine formula, easily the most cited, was published in 1974 as a way of calculating drug dosages — specifically gentamicin — for patients whose actual weight would have produced dangerous doses. It was never validated as a measure of the weight at which a person is healthiest. Hamwi's, a decade earlier, came out of diabetes management.

They persist because they are quick, need only height, and work well enough for the clinical jobs they were designed for: dosing, ventilator tidal volume, and estimating renal function. Treating them as an aesthetic or wellness goal is a misuse that their authors would not recognise.

What to use instead

If your aim is health rather than pharmacology, the useful signals are:

  • The healthy BMI range for your height — a band of several kilograms, not a single number. Our BMI calculator gives it.
  • Waist-to-height ratio, ideally below 0.5. It predicts cardiometabolic risk better than BMI and needs one tape measurement. See the calculator here.
  • Body composition — the ratio of fat to lean mass, which no height-based formula can see. Our body fat calculator estimates it from tape measurements.
  • Function and markers — blood pressure, lipids, fasting glucose, sleep quality, how you feel climbing stairs. These matter more than any target weight.

Frame weight as a range you feel and function well in, not a figure to hit. Two people of the same height can both be healthy 12 kg apart.

Frequently asked questions

Which formula is the most accurate?

None of them, because none was designed to be. They were built for clinical dosing, not health assessment. If you must pick one, Devine is the most widely used; but the healthy BMI range is a more defensible answer for non-clinical purposes.

Why do they ignore body frame size?

Simplicity. Frame size does affect healthy weight — measured by elbow breadth or wrist circumference, a large-framed person can carry several kilograms more at the same height — but adding it would have made bedside calculation harder, which defeated the purpose.

Do they work for athletes?

Poorly. Like BMI, they cannot see muscle. A muscular athlete will routinely exceed all four figures while carrying very little fat. Body composition is the relevant measure there.