Ideal Weight Calculator

What It Does

Give your height and sex and this page returns six published estimates of ideal body weight — Devine, Robinson, Miller, Hamwi, Peterson and Broca — beside the healthy weight range for your height, which is the BMI band of 18.5 to 25 applied to your own height. Seeing the six together is the point: for a man of 180 cm they span 8.5 kg, from 71.5 kg to 80.0 kg. A target band, the central half of the healthy range, is derived from the band rather than from any formula.

Real-World Usage

Doctors reach for these formulas when a number has to be pinned to something: Devine is still the reference for dosing drugs that distribute in lean tissue, and hospital dietitians use an ideal body weight to set a feeding target for a patient who cannot be weighed. In a gym the band matters more than the formulas — a calorie or protein target usually starts from body weight, and the band tells you which weights are worth aiming at. For everyone else the useful habit is comparison with yourself over time: pick a weight inside the band, then judge it by what happens over four to six weeks.

Local Context

The formulas are used unchanged everywhere: none was refitted per country, and no health service publishes its own constants. In practice the differences are the units and the guidance around them. The United States and Canada record height in feet and inches and weight in pounds, while continental Europe, the United Kingdom and Latin America use centimetres and kilograms, which is why this page converts the band into your own units. Where countries do diverge is in what they do with the band: the NHS pairs BMI with waist-to-height ratio, and Canadian guidance adds waist circumference above a BMI of 25. The formulas themselves are identical in all of them.

Why the Formulas Disagree

Each equation was fitted on a different population and for a different job. Devine (1974) was derived from hospital patients so that drug doses could be scaled to lean tissue; Robinson (1983) and Miller (1983) tested it against wider populations and both came out lower. Hamwi (1964) came from dietetic practice and runs steeper, so it reads highest of the four for tall people. Peterson (2016) works the other way round — it takes a healthy BMI of 22 and asks what weight that is at your height, which is why it lands near the middle of the band. Broca (1871) is a nineteenth-century rule of thumb that the others replaced; it is printed here because the calculators people compare us with print it. None was fitted on a sample that looks like any one reader, and for an individual they are all rough.

A Range, Not a Number

The honest answer to “what should I weigh?” is a range. BMI 18.5 to 25 is the band with the evidence behind it for adults, and it is wide: about 21 kg at 180 cm. Where you sit inside it depends on muscle, frame and age, none of which the formulas see. That is why the target band on this page is derived from the healthy range — the middle half of it, with a margin to both thresholds — and not from the formulas: two people of the same height with the same six estimates can have very different body composition. Pick a weight inside the band, then let four to six weeks of real measurement, not this page, tell you whether it is right for you.

Where These Numbers Stop

These formulas take height and sex, nothing else. They were built for adults, so they do not apply to children or teenagers. They are inaccurate in pregnancy and in anyone with a lot of muscle, and they say nothing about thyroid disease, medication, eating disorders, body frame or where fat sits — which matters more to health than the total. The formulas also extrapolate below five feet, where they read low, and Broca is printed for comparison rather than as guidance. This page is an educational estimate, not medical advice: if your weight is a health concern, talk to a clinician who can measure you rather than a formula that cannot.

What is my ideal weight?

There is no single number. The published formulas disagree by several kilograms for the same person, and healthy weight is a range: for an adult it runs from BMI 18.5 to 25 applied to your height, which on this page is the healthy weight range shown above. Treat the formulas as estimates and the range as the target.

Why do the ideal weight formulas give different answers?

Each was fitted on a different group of people and for a different purpose. Devine (1974) came from hospital patients and is used for drug dosing, Robinson (1983) and Miller (1983) were corrections to it, Hamwi (1964) came from dietetics, Peterson (2016) starts from a healthy BMI, and Broca (1871) is a rule of thumb. Different samples, different answers.

Is ideal weight the same as healthy weight?

No. An ideal weight is one formula's single estimate for your height; a healthy weight is the range in which a BMI between 18.5 and 25 puts you. The range is wider, it is the part with evidence behind it, and it is what this page leads with.

Does ideal weight change with age or muscle?

These formulas see neither. They take height and sex only, so a muscular athlete and a sedentary adult of the same height get the same numbers. Muscle is denser than fat, so anyone carrying a lot of lean mass will read above the range while being perfectly healthy. Use body-fat percentage or lean body mass alongside it.