Ideal Weight Calculator

How this is calculated

Devine: 50 kg (M) / 45.5 kg (F) + 2.3 kg per inch over 5 ft · Range: 18.5–24.9 × height(m)²

Worked example: male, 180 cm → 10.87 inches over five feet, so 50 + 2.3 × 10.87 = 75.0 kg (165 lb). The healthy-BMI band for that height runs 59.9–80.7 kg — a 20-kg-wide corridor, which is exactly why the single number should be read as a landmark, not a destination. Not medical advice.

Four formulas, four answers, and why we show them all

There is no medical consensus on ideal body weight, and this page does not pretend otherwise. The four formulas shown were written between 1964 and 1983 by different authors for different purposes, and they can differ by five kilograms or more for the same person. Hamwi (1964) was created to set diabetic diet targets quickly. Devine (1974) was written to calculate drug doses, not to describe health, and remains the most-used precisely because pharmacology adopted it. Robinson (1983) and Miller (1983) were both attempts to correct Devine against better population data, and they disagree with each other.

All four share an awkward inheritance: each defines a base weight at five feet and adds a fixed amount per inch above it, which makes them imperial in structure, linear in a way real bodies are not, and less reliable the further you are from average height. Showing the spread rather than picking a winner is the honest presentation, and the width of that spread is the most informative thing on the page — it tells you the concept itself is imprecise, and that any weight inside the range is defensible.

What these formulas ignore

Every one of them uses only height and sex. None accounts for frame size, though wrist and elbow breadth genuinely vary skeletal weight by several kilograms between people of identical height. None accounts for muscle, so a trained body will exceed all four targets while being in excellent health. None accounts for age, though a modest increase in weight through middle age is associated with better outcomes than staying at a twenty-year-old's weight, particularly for bone density. And none was derived from a population resembling the world's diversity of builds.

A more useful way to think about a target

Rather than a single ideal, most clinicians now work with a healthy range, and the evidence supports that. Weight stability matters more than any particular figure: repeated cycles of loss and regain are associated with worse outcomes than remaining stable at a higher weight. Where you carry weight matters more than how much — the waist measurement is a better predictor of metabolic risk than total mass. And fitness matters independently of weight, to the point where an active person at a higher weight often has better outcomes than a sedentary person at a "correct" one.

If you want a number to aim at, take the range these formulas span, cross-check it against the healthy BMI range for your height, and pick something inside the overlap that you can hold without misery. A target you sustain beats a target you reach twice.

Where the formulas are genuinely the right tool

Ideal body weight has one setting where it is not a rough guide but a working necessity: clinical dosing. Some drugs distribute through lean tissue rather than fat, so dosing on actual weight would overdose a heavier patient — anaesthetic agents, certain antibiotics and mechanical-ventilation tidal volumes are all set from predicted body weight for exactly this reason. That is why Devine's 1974 formula, written for pharmacy, remains embedded in hospital software half a century later, and why it should not be mistaken for advice about what you personally ought to weigh.