Ideal weight calculator
Four different formulas, because there is no single agreed answer. Seeing how much they disagree is itself informative — the spread tells you how soft the concept of an ideal weight really is.
Built by Mubashir. Uses a published standard formula, named below. Not medical advice — see the limitations section.
Your details
Wrap your thumb and middle finger round the opposite wrist: overlapping suggests small, touching medium, not meeting large.
Average across four formulas
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Range across formulas
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Healthy BMI weight range
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Average in pounds
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| Formula | Kilograms | Pounds |
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Show the working
—These formulas were not designed to tell you what to weigh. Most were developed for clinical drug dosing, not health guidance, and none accounts for muscle mass, bone density, age or ancestry. Body composition matters more than the number on a scale. If weight is a concern, discuss it with a doctor or registered dietitian rather than working toward a formula's output.
Where these formulas came from
This is the part most calculators omit, and it changes how much weight the results deserve.
The Devine formula, published in 1974, was created to estimate drug dosages — specifically to standardise how much of certain medications a patient should receive. It was never validated as a health target. It became a general-purpose ideal weight formula largely by accident, because it was simple and already in circulation.
The Hamwi formula came from 1964 and was intended for calculating dietary needs of patients with diabetes. Robinson and Miller, both from 1983, were attempts to correct Devine against actual population data.
All four take the same shape: a base weight for a person of five feet, plus a fixed increment for each additional inch. That structure means they behave poorly at the extremes of height, and none of them was derived from health outcomes.
Why the four disagree
Run the calculator and look at the spread. For most heights the formulas differ by several kilograms, and there is no principled basis for preferring one.
That spread is the honest answer to the question. There is no single ideal weight for a given height, and the fact that four serious attempts to define one produce four different numbers should be read as evidence that the concept is soft rather than as a reason to average them.
The healthy BMI range shown alongside is usually wider than all four formulas, and is derived from population mortality data rather than dosing convenience. It is arguably the more defensible figure, though it inherits every limitation of BMI itself.
What the formulas cannot see
Muscle mass, which is the largest omission. A trained person can be well above every formula's output and carry low body fat. Since muscle is denser than fat, gaining it while losing fat can leave weight unchanged or higher while health improves in every measurable respect.
Frame size is handled here as a crude ten percent adjustment either way, which is better than ignoring it and far from precise. Bone density, limb proportions, age and ancestry are not accounted for at all — and body composition standards do differ meaningfully across populations.
A more useful set of questions
Rather than aiming at a number, the measures that track health more closely are your waist-to-height ratio, which is a simple screen where under half your height is generally favourable; blood pressure; resting heart rate; and how you actually feel and function day to day.
A weight at which you sleep well, move comfortably and maintain stable blood work without constant effort is closer to an ideal weight than anything a 1974 dosing formula can tell you.
Frequently asked questions
Is ideal weight the same as healthy weight?
No. Ideal weight formulas produce a single number from height and sex, while a healthy weight is a range that depends on body composition, fitness and medical history. The healthy BMI range is usually wider than any of these formulas.
Why do the four formulas give different answers?
Because they were developed independently, for different purposes, against different populations. Devine and Hamwi were designed for clinical dosing rather than health targets. The disagreement reflects genuine uncertainty in the concept.
Which formula should I use?
None of them as a target. If you want a single reference, the healthy BMI range shown alongside is derived from population health outcomes rather than dosing convenience, which makes it more defensible.
How do I determine my frame size?
Wrap your thumb and middle finger around the opposite wrist. Overlapping fingers suggest a small frame, just touching a medium one, and not meeting a large one. This is approximate.
What about athletes?
These formulas will substantially underestimate an appropriate weight for anyone carrying significant muscle, because they cannot distinguish lean tissue from fat. A body composition measurement is far more informative.
Does ideal weight change with age?
The formulas say no, which is one of their limitations. In practice, body composition shifts with age as muscle mass declines, and some evidence suggests a slightly higher BMI is not disadvantageous in older adults.