Ideal Weight Calculator

Four formulas dominate the literature on ideal body weight — Devine, Robinson, Miller and Hamwi — and they disagree with each other by several kilograms at the same height. That disagreement is the most informative thing about them. None was derived from health outcomes; they were built for clinical purposes such as drug dosing and ventilator settings, where a standardised figure matters more than a physiologically meaningful one. This calculator runs all four and shows the spread, because the range they produce is a far more honest answer than any single number. Treat it as a rough zone rather than a target. Body composition, frame size and what you can maintain without misery all matter more than hitting a figure a formula produced from height alone.

How this is calculated

All four formulas share a structure: a base weight at 152 cm (5 feet), plus a fixed increment per additional inch of height, with different constants for men and women.

Devine, the most widely used, sets men at 50 kg + 2.3 kg per inch over 5 feet, and women at 45.5 kg + 2.3 kg per inch. Robinson uses 52 kg + 1.9 kg for men and 49 kg + 1.7 kg for women. Miller uses 56.2 kg + 1.41 kg and 53.1 kg + 1.36 kg. Hamwi uses 48 kg + 2.7 kg and 45.5 kg + 2.2 kg.

Worked example for a man at 180 cm, which is about 11 inches over 5 feet: Devine gives 75.3 kg, Robinson 72.9 kg, Miller 71.7 kg and Hamwi 77.7 kg. A six-kilogram spread from the same height.

Why the formulas disagree by so much

They were developed independently, decades apart, for different purposes and from different populations. Devine's came from pharmacokinetics in 1974 — it exists so that drug doses can be standardised, not so that people can set weight goals. Hamwi's dates from 1964 and was intended for diabetic diet planning.

None of them incorporates frame size, muscle mass or body composition, and all of them are linear in height, which real human proportions are not. At the extremes of height they become noticeably less plausible in both directions.

What to use instead

A BMI range is a more defensible target zone than any single ideal weight: the normal range of 18.5 to 24.9 at 180 cm corresponds to roughly 60 to 81 kg, which is wide because healthy weight genuinely is.

Beyond that, waist-to-height ratio and body fat percentage tell you more about health than total weight does. Two people at the same weight and height can differ enormously in composition, and the one carrying more muscle is generally in better metabolic shape despite the identical number on the scale.

How to use the ideal weight calculator

Enter your height and sex. These are the only inputs any of the four formulas use — which is itself a reason not to over-trust the output.
Read the spread, not one figure. The gap between the highest and lowest formula is typically several kilograms. That range is the honest answer.
Cross-check against a BMI range. The healthy BMI band at your height gives a wider and better-grounded target zone than any single ideal-weight number.

Frequently asked questions

Why do the formulas disagree?

Each was fitted to different clinical populations decades apart. The healthy-BMI range (18.5–24.9) is the more evidence-based guide; the formulas remain popular for medication dosing.

Which ideal weight formula is most accurate?

None of them is accurate in the sense people mean, because none was derived from health outcomes. Devine is the most widely used, but it exists to standardise drug dosing rather than to describe a healthy weight. Use the spread across all four as a rough zone.

Do these formulas account for muscle or frame size?

No. Every one of them uses height and sex alone. A heavily muscled person and a sedentary person of the same height receive the same ideal weight, which is the clearest illustration of the limitation.

What should I use instead?

A healthy BMI range gives a wider and better-grounded target — at 180 cm that is roughly 60 to 81 kg. Waist-to-height ratio and body fat percentage say more about health than total weight does at any given height.