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Ideal Body Weight Formulas: Devine, Robinson and Miller Compared

By HealthToad Editorial · Last updated 24 Oct 2026 · 7 min read

Type your height into an ideal body weight calculator and you will get a neat number, often to a decimal place, that looks like a scientific verdict on what you should weigh. It is not. The classic formulas behind that number were created for practical, limited purposes — originally to estimate drug dosages — and they use only your height and sex, ignoring muscle, bone, age, build and health. They are useful as rough reference points, but they become misleading the moment they are treated as ideals to chase at any cost.

This guide compares the three formulas you will meet most often — Devine, Robinson and Miller — explains where each came from, shows how much they differ for the same person, and explains what a sensible range looks like instead of a single magic number. If you have ever been confused by getting three different answers from three calculators, the explanation is here. Compare the formulas for your height with the Ideal Body Weight Calculator while you read.

Where the formulas came from

The Devine formula, published in 1974, was created to calculate drug doses: doctors needed a standard weight to scale certain medicines, particularly for patients whose actual weight might distort dosing. It assigns 50 kilograms for a man of five feet, 45.5 kilograms for a woman of five feet, and adds 2.3 kilograms for every inch above five feet. Robinson's formula, from 1983, uses the same five-foot bases but adds 2.3 kilograms per inch for men and 2.2 for women, with slightly different rounding in some versions. Miller's formula, also from 1983, uses larger base weights — 56.2 kilograms for men and 53.1 for women at five feet — but smaller increments of 1.41 and 1.36 kilograms per inch.

None of these was derived by studying which weight makes people healthiest over a lifetime. They were conveniences: simple arithmetic a clinician could do at a bedside before electronic records. Their persistence in calculators reflects that simplicity, not superior accuracy. Later formulas, such as Hamwi and Broca, follow the same height-only logic with different constants, and they produce yet more answers. When several respectable formulas disagree, that disagreement itself is information: the concept of a single ideal weight is shakier than the decimal places suggest.

How much do they actually differ?

At average heights the formulas converge closely, often within a kilogram or two, which is why they feel authoritative. At taller heights they diverge more, with Miller giving lower weights than Devine and Robinson because its per-inch increment is smaller. At shorter heights the pattern reverses, with Miller giving higher weights. The practical lesson is to treat any formula output as the centre of a range of at least plus or minus five kilograms, wider if you are muscular, broad-framed or older, rather than as a target to hit precisely.

Frame size illustrates why. Two people of the same height can have very different bone structures: wrist circumference, shoulder width and natural build all affect how much weight a frame carries comfortably. The old Metropolitan Life insurance tables tried to account for small, medium and large frames, and modern body composition measures do the job better, but height-only formulas cannot. A broad-framed, muscular person at five kilograms above a formula weight may be perfectly healthy, while a slight-framed person at the formula weight may carry excess fat.

What ideal weight gets wrong

The word ideal is the problem. It implies a single best weight, independent of context, when health depends on composition, distribution, fitness and medical history. A weight that is ideal for a sedentary person with diabetes risk may be too low for an athlete, and a weight that looks ideal on a chart may be unsustainable for someone whose appetite, work and family life pull elsewhere. The formula also ignores age: older adults often do better slightly heavier than younger adults, because a small reserve protects against illness, falls and frailty, provided muscle is maintained.

Drug dosing, the original purpose, shows the limits clearly. Modern dosing increasingly uses adjusted or lean body weight for people with obesity, because using a height-only ideal weight can under-dose, while using actual weight can over-dose. Clinicians therefore treat these formulas as one input among several, adjusted for the individual. If doctors do not trust a formula alone for a medicine dose, it makes little sense for the rest of us to trust it alone for a life goal.

Using the formulas sensibly

Use an ideal weight result as a conversation starter, not a verdict. Compare it with your BMI range, your waist circumference, your body fat estimate and your fitness, and look for agreement or disagreement. If all measures point the same way — for example, formula weight, BMI and waist all suggest excess fat — then gradual fat loss is a sensible goal. If they disagree — formula says overweight, but waist is small, body fat is healthy and you are strong — then the formula is probably the measure that is wrong for you.

• Take the formula result as a range, roughly plus or minus 10 percent, not a single number.
• Check waist and body composition before acting on a formula alone.
• Consider frame, muscle and age: muscular, broad or older people often sit healthily above formula weight.
• Set goals in terms of behaviours and health markers, not just a scale number.
• Discuss significant weight targets with a clinician, especially with medical conditions or medicines.

For people who do decide to move towards a formula range, the pace matters more than the precision of the target. Losing half a kilogram a week while preserving muscle through protein and resistance training, and reassessing waist, strength and energy along the way, is far healthier than crash dieting to a decimal-place target and arriving weaker. The target can move as you learn what your body sustains comfortably.

Common mistakes

The most common mistake is averaging several formula results and treating the average as more scientific than any single one; averaging guesses does not remove their shared flaw, which is ignoring composition. Another is using ideal weight to judge others, particularly children, athletes or older adults, for whom height-only formulas are least appropriate. A third is pursuing an ideal weight from adolescence or from a different stage of life, ignoring that bodies, responsibilities and health priorities change.

• Treating a formula output as a precise prescription to hit exactly.
• Ignoring muscle, frame and waist when the formula disagrees with them.
• Using one formula for drug dosing or medical decisions without clinical advice.
• Setting an ideal weight from a younger, lighter version of yourself as the only acceptable outcome.
• Judging health or attractiveness from a height-only number.

The short version

Devine, Robinson and Miller are simple height-based estimates created for dosing, not destiny. They agree closely at average heights and diverge at extremes, and all of them ignore muscle, frame, age and fat distribution. Use them as a rough centre of a wide range, check them against waist, body fat and fitness, and set goals you can sustain with strength intact. A healthy weight is a range you live in comfortably, not a single number a formula hands you.

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