What is the Devine formula for ideal body weight?

For men: 50 kg + 2.3 kg for every inch of height over 5 feet. For women: 45.5 kg + 2.3 kg per inch over 5 feet. B.J. Devine published it in 1974 as a way to estimate lean-ish body weight for calculating doses of the antibiotic gentamicin — not as a weight target. It remains the standard equation behind medication dosing and ventilator settings.

Why do the ideal weight formulas give different answers?

Because they were derived by different people, in different decades, for different purposes — Hamwi (1964) from a clinical diabetes handbook, Devine (1974) for drug dosing, Robinson and Miller (both 1983) as refits against actuarial height-weight data. They share the same structure (a base weight at 5 feet plus an increment per inch) but use different constants, so for the same height they disagree by several kilograms.

Is ideal body weight accurate?

Not as a personal target, because “accurate” isn't really the right frame. The equations are population-level estimates that ignore frame size, muscle mass, body composition, and age, and they disagree with each other by 3–6 kg for the same person. They are accurate enough for what they were built for — standardizing medication doses and ventilator volumes to height — and too crude for judging an individual body.

What is the ideal weight for my height?

There is no single number. For a 175 cm man the four classic formulas give roughly 68.8 to 72.0 kg, and the WHO healthy-BMI range (18.5–24.9) spans about 57 to 76 kg — a 19 kg window. A weight that is healthy for you depends on body composition, muscle mass, age, and health markers, which is a conversation for a clinician, not a formula.

Is a healthy BMI better than an ideal weight formula?

For general context, yes — a range is more honest than a point. Mapping the WHO's 18.5–24.9 BMI band to your height gives a span of healthy-associated weights instead of one false-precision number. But BMI inherits the same core limitation: it can't see body composition, so a muscular person can sit “over” the range while lean. Both are screening context, not verdicts.

Guide

Ideal weight formulas: where Devine, Robinson, and Hamwi came from — and what they're actually for

The most-quoted “ideal weight” formula in the world was written to dose gentamicin, not to grade bodies.

By Buğra SözeriPublished July 17, 2026

Type “ideal weight” into a search box and you get a single confident number — usually from a formula named Devine, Robinson, Miller, or Hamwi. What almost no result mentions is that none of these equations was designed to tell anyone what they should weigh. They came from antibiotic dosing, a diabetes handbook, and life-insurance tables, and their real modern home is the pharmacy and the intensive-care unit. This guide covers where each formula actually came from, how much they disagree, and what a more honest answer to “what should I weigh?” looks like. It is educational only — not medical or dietary advice.

Where the formulas actually came from

The full history is documented in Pai and Paloucek’s 2000 review, The origin of the “ideal” body weight equations, and it is stranger than the formulas’ reputation suggests.

Hamwi (1964) is the oldest. G.J. Hamwi published his rule of thumb in a clinical handbook on diabetes management — a quick bedside estimate for clinicians setting dietary targets, offered without a derivation from outcome data.

Devine (1974) is the famous one, and its origin is the punchline: B.J. Devine proposed it in a paper about dosing gentamicin, an antibiotic that distributes mainly into lean tissue rather than fat. Dosing by actual weight overdoses heavier patients, so Devine needed a height-based stand-in for lean-ish body weight. The equation was a pharmacokinetic convenience. It escaped the pharmacy, and fifty years later it powers half the “ideal weight” results on the internet.

Robinson and Miller (both 1983)are corrections, not independent ideas. Both teams refit Devine-style equations against actuarial height-weight data — the Metropolitan Life insurance tables that related body size to mortality in policyholders — because Devine’s constants had been proposed largely without empirical validation. Robinson’s version runs lighter at tall heights; Miller’s starts heavier at five feet and climbs more slowly.

All four share one skeleton: a base weight at 5 feet (60 inches), plus a fixed increment per inch of height above that. Devine adds 2.3 kg per inch for both sexes; Hamwi adds 2.7 (men) and 2.2 (women); Robinson 1.9 and 1.7; Miller just 1.41 and 1.36. Below 5 feet the equations are simply undefined — extrapolating downward eventually produces negative weights, which is a useful reminder of how mechanical they are.

Same height, four answers

Because the constants differ, the formulas disagree — not subtly. For a 175 cm man (about 8.9 inches over 5 feet):

Devine: 50 + 2.3 × 8.9 ≈ 70.5 kg
Robinson: 52 + 1.9 × 8.9 ≈ 68.9 kg
Miller: 56.2 + 1.41 × 8.9 ≈ 68.7 kg
Hamwi: 48 + 2.7 × 8.9 ≈ 72.0 kg

For a 165 cm woman (about 5.0 inches over 5 feet):

Devine: 45.5 + 2.3 × 5.0 ≈ 56.9 kg
Robinson: 49 + 1.7 × 5.0 ≈ 57.4 kg
Miller: 53.1 + 1.36 × 5.0 ≈ 59.8 kg
Hamwi: 45.5 + 2.2 × 5.0 ≈ 56.4 kg

A spread of roughly 3 kg both times — and the gaps widen with height, since the per-inch increments diverge. Four equations, each presented somewhere on the internet as the ideal weight formula, disagreeing about the same body by the weight of a house cat. If a question has four confident answers, the useful information is the range, not any single number.

The BMI-range alternative

A more defensible way to relate weight to height is to skip the single number entirely and map the WHO’s healthy-associated BMI band — 18.5 to 24.9 — onto your height: multiply each bound by height in metres squared. At 175 cm that gives roughly 57 to 76 kg; at 165 cm, roughly 50 to 68 kg. Notice that every formula result above lands comfortably inside its band — the four equations are, in effect, arguing over where to place a point inside a 19 kg window. The range framing is more honest about the underlying uncertainty, though BMI carries its own well-documented blind spots, which our guide to BMI’s accuracy covers in detail.

Why a single “ideal” number is a category error

The deeper problem isn’t which formula is best — it’s that the question assumes height determines what a body should weigh. It doesn’t. Two people of identical height can differ substantially in frame size, bone density, muscle mass, and fat distribution, and those differences — not the scale reading alone — are what matter for health. A muscular 175 cm athlete can sit well above every formula’s output while carrying less body fat than someone the formulas approve of; the distinction between weight and composition is the subject of our BMI vs body fat comparison. Age shifts the picture too: body composition and the weight ranges associated with the best health outcomes change across adulthood, while the formulas return the same answer at 25 and at 75. A height-only equation cannot see any of this. That is not a flaw to patch with a fifth formula — it is the reason a single ideal number was never a coherent target in the first place.

What the formulas are still legitimately for

None of this makes the equations useless — it returns them to their day jobs, where they perform well.

Medication dosing.Devine’s original purpose is still live: drugs that distribute mainly into lean tissue are dosed from ideal or adjusted body weight rather than actual weight, so a heavier patient isn’t overdosed on the basis of tissue the drug never reaches. Here the formula isn’t judging anyone’s body; it is standardizing a calculation to height.

Mechanical ventilation. Lung size scales with height, not with total body weight. The landmark ARDS Network trial published in the New England Journal of Medicine in 2000 set ventilator tidal volumes at 6 ml per kilogram of predicted body weight— a Devine-style height-and-sex equation — and cut mortality from 39.8% to 31.0% compared with 12 ml/kg. Every ICU ventilator set to lung-protective volumes today is quietly running an ideal-body-weight formula. It is arguably the most consequential thing these equations have ever done, and it has nothing to do with anyone’s appearance.

When to ignore them

Ignore the formulas whenever the question is really about you rather than about standardizing a clinical calculation: setting a personal weight goal, judging your progress in the gym, or deciding whether your current weight is a problem. For those questions, a height-only estimate from 1974 has nothing individual to offer, and treating its output as a verdict can do real harm — particularly for anyone with a difficult relationship with weight. If you want a personal assessment, that comes from a clinician who can consider your composition, history, and health markers together. The classic formulas are best read the way their authors intended: as rough population math, built for prescriptions and ventilators — useful in the hospital, and safely ignorable on the bathroom scale.

Frequently asked questions

What is the Devine formula for ideal body weight?: For men: 50 kg + 2.3 kg for every inch of height over 5 feet. For women: 45.5 kg + 2.3 kg per inch over 5 feet. B.J. Devine published it in 1974 as a way to estimate lean-ish body weight for calculating doses of the antibiotic gentamicin — not as a weight target. It remains the standard equation behind medication dosing and ventilator settings.
Why do the ideal weight formulas give different answers?: Because they were derived by different people, in different decades, for different purposes — Hamwi (1964) from a clinical diabetes handbook, Devine (1974) for drug dosing, Robinson and Miller (both 1983) as refits against actuarial height-weight data. They share the same structure (a base weight at 5 feet plus an increment per inch) but use different constants, so for the same height they disagree by several kilograms.
Is ideal body weight accurate?: Not as a personal target, because “accurate” isn't really the right frame. The equations are population-level estimates that ignore frame size, muscle mass, body composition, and age, and they disagree with each other by 3–6 kg for the same person. They are accurate enough for what they were built for — standardizing medication doses and ventilator volumes to height — and too crude for judging an individual body.
What is the ideal weight for my height?: There is no single number. For a 175 cm man the four classic formulas give roughly 68.8 to 72.0 kg, and the WHO healthy-BMI range (18.5–24.9) spans about 57 to 76 kg — a 19 kg window. A weight that is healthy for you depends on body composition, muscle mass, age, and health markers, which is a conversation for a clinician, not a formula.
What is ideal body weight used for in medicine?: Two main things. Dosing: some drugs distribute mainly into lean tissue, so doses are calculated from ideal or adjusted body weight rather than actual weight. Mechanical ventilation: lung size scales with height, not weight, so safe tidal volumes are set at 6 ml per kg of predicted body weight — a Devine-style, height-based equation — which the ARDS Network trial showed reduces mortality.
Is a healthy BMI better than an ideal weight formula?: For general context, yes — a range is more honest than a point. Mapping the WHO's 18.5–24.9 BMI band to your height gives a span of healthy-associated weights instead of one false-precision number. But BMI inherits the same core limitation: it can't see body composition, so a muscular person can sit “over” the range while lean. Both are screening context, not verdicts.

Sources & references

Authoritative references cited by this piece. Verified by Buğra Sözeri on the dates shown and re-checked at every deploy.

Pai MP, Paloucek FP — The origin of the “ideal” body weight equations. Annals of Pharmacotherapy, 2000 — The definitive historical review of where the Devine, Robinson, Miller, and Hamwi equations came from and what they were derived for(as of 2026-07-17)
ARDS Network — Ventilation with lower tidal volumes for acute lung injury and ARDS. NEJM, 2000 — The landmark trial that set ventilator tidal volumes per kilogram of predicted body weight — the Devine-style equations' most important modern use(as of 2026-07-17)
World Health Organization — Obesity and overweight fact sheet — The WHO's BMI thresholds for adults, which the BMI-range alternative to single-number formulas is built on(as of 2026-07-17)

Published July 17, 2026