Ideal Body Weight Formulas, Compared

By Longevity Lab · Published: August 23, 2026

Based on peer-reviewed research — full source list at the end of this article. This is educational information, not medical advice.

The classic ideal body weight formulas — Devine, Robinson, Miller and Hamwi — return a single number for a given height and sex, and they disagree with each other by up to five kilograms at the same height. None of them was designed to describe health. Devine’s was written in 1974 to calculate gentamicin doses, and the Hamwi figures came from insurance actuarial tables. A Ideal body weight figure is useful in the settings that created it, and misleading almost everywhere else.

The four formulas

Each takes the same shape: a base weight for 5 feet, plus a fixed increment per additional inch.

At 1.80 m (71 inches) for a man, that produces 77.7 kg by Hamwi, 75.3 kg by Devine, 73.9 kg by Robinson and 71.7 kg by Miller — a spread of 6 kg between formulas that all claim to name the ideal.

The disagreement is not a defect in any one of them. They were fitted to different reference populations for different purposes, and there was never a single quantity they were all estimating.

Where they came from, and what for

Devine’s equation was published in a pharmacy journal as a way to scale aminoglycoside doses, because those drugs distribute through lean tissue and dosing on total body weight overdoses heavier patients. It is still used for that, and still appropriate for it.

Hamwi’s figures came from the Metropolitan Life insurance tables, which were built from policyholder data — a self-selected, largely white, largely middle-class population measured in shoes and clothing. Robinson and Miller were later attempts to refit the same idea to better data.

So the honest description is: these are dosing and actuarial tools that acquired a second life as health advice they were never validated for. Nobody has shown that people at their Devine weight live longer than people two kilograms away from it.

Why a range beats a number

The mortality evidence does not describe a point. It describes a wide, flat basin between BMI roughly 20 and 25, inside which weight is not the variable that moves outcomes. At 1.80 m that basin runs from about 65 kg to 81 kg — sixteen kilograms in which the data does not distinguish.

A single “ideal” number inside that basin implies a precision that does not exist, and it creates a target that most people miss by definition. A range invites the more useful question: am I inside it, and if not, by how much?

There is a modern equation that acknowledges this. Peterson and colleagues published a universal formula in 2016 that returns the weight corresponding to any chosen BMI at a given height, rather than one privileged value — weight = BMI × height² is really all it is, which is the point. Choose your target BMI, and the arithmetic follows. Our BMI calculator prints the whole 18.5–24.9 range in kilograms for your height, which is the same information without the false precision.

What the formulas systematically miss

Frame size, for one. The old insurance tables at least had small, medium and large frame columns; the formulas dropped them. Elbow breadth or wrist circumference still varies by several centimeters between adults of the same height, and it corresponds to real differences in skeletal mass.

Fat-free mass (FFM), for another, which is the variable that actually matters and the one none of these equations contains. Two men at 1.80 m, one at 78 kg with 14% body fat and one at 78 kg with 28%, are identical to every formula on the table above.

And age. All four return the same figure at 25 and at 75, while the evidence says the healthy band shifts upward in later life. Body composition assessment at least splits the mass into its components, which is the information the formulas throw away.

A better way to set a weight goal

1. Start from a percentage, not a destination. Clinical guidelines target 5–10% of current body weight, because that is the amount associated with measurable improvements in blood pressure, triglycerides and glucose — and it is maintainable.
2. Check the waist alongside. If waist falls and weight does not, the intervention is working. That happens routinely when resistance training is involved.
3. Use the BMI range as a boundary, not a target. Knowing you are 6 kg above the top of the healthy band is more actionable than knowing you are 9 kg from an ideal.

The Body Mass Index (BMI) tool reports the healthy weight range for your height alongside the adjustment needed to reach it, which is the presentation that matches what the evidence can actually support.

Frequently asked questions

Sources

Disclaimer. This article is for information only and does not replace medical advice. Talk to a qualified clinician before changing anything about your health.