Ideal Weight Calculator
See what the four classic ideal-body-weight formulas — Devine, Robinson, Miller, and Hamwi — suggest for your height and sex, shown as a range rather than a single misleading number. Results in kg or lb to match your chosen units.
Ideal-weight range
Example: male at 175 cm → Devine 70.5 kg.
Four formulas, four answers, one height
Enter a height and this page returns four numbers rather than one. For a man at 175 cm the engine computes Devine 70.5 kg, Robinson 68.9 kg, Miller 68.7 kg, and Hamwi 72 kg — 3.3 kg between the highest and the lowest, from a single input all four were given equally. Nothing has gone wrong. The four rules were built separately and they disagree with each other by design, which is why all four are reported instead of averaged into one confident-looking figure.
All four originated decades ago in clinical contexts; the Devine formula was proposed for drug dosing. Mechanically, what they are is four straight lines through height. Each takes exactly two inputs — a height and a sex — and returns one weight in kilograms. It has nothing to say about the person that height belongs to, because nothing about that person was ever passed to it.
The shape all four share
Every one of the four is the same two-part rule: a base weight at 5 ft (152.4 cm), plus a fixed increment for each inch of height above that floor. What separates them is only the pair of constants dropped into that shape — where the line starts, and how steeply it rises — with a separate pair for each sex. The constants are recoverable from the engine itself. Ask it for a height of exactly 152.4 cm and every formula is sitting on its base value with zero increments added; ask again at 154.94 cm, the floor plus one inch, and each returns its base plus exactly one increment. Subtract the first from the second and both numbers fall out:
| Formula | Base at 152.4 cm, male | Per inch, male | Base at 152.4 cm, female | Per inch, female |
|---|---|---|---|---|
| Devine | 50 kg | 2.3 kg | 45.5 kg | 2.3 kg |
| Robinson | 52 kg | 1.9 kg | 49 kg | 1.7 kg |
| Miller | 56.2 kg | 1.41 kg | 53.1 kg | 1.36 kg |
| Hamwi | 48 kg | 2.7 kg | 45.5 kg | 2.2 kg |
Reading down a per-inch column is the disagreement in miniature. Hamwi climbs fastest per inch of height and Miller slowest, so the gap between those two lines widens with every inch travelled away from wherever they happen to cross. Reading down a base column supplies the other half of the story: the line that starts highest is not the line that rises fastest, and that mismatch is what makes the ordering of the four results unstable.
Note what is absent from the table. There is no coefficient for anything but height, and no column for anything but sex. As implemented here, those two constants per sex are the entire specification of each rule — there is nothing else in the function to print.
The disagreement is the output
Because the four lines have different slopes, they cross. Which formula reports the largest number is therefore not fixed; it depends on the height entered. Same engine, same code the form runs in your browser, five heights, male:
| Height | Lowest of the four | Highest of the four | Spread |
|---|---|---|---|
| 152.4 cm | 48 kg (Hamwi) | 56.2 kg (Miller) | 8.2 kg |
| 160 cm | 56.1 kg (Hamwi) | 60.4 kg (Miller) | 4.3 kg |
| 170 cm | 65.2 kg (Robinson) | 66.7 kg (Hamwi) | 1.5 kg |
| 180 cm | 71.5 kg (Miller) | 77.3 kg (Hamwi) | 5.8 kg |
| 190 cm | 77.1 kg (Miller) | 88 kg (Hamwi) | 10.9 kg |
At 170 cm the four land within 1.5 kg of one another and the choice between them barely registers. At 190 cm they span 10.9 kg, and the choice of formula is most of the answer. The ranking flips across the table as well: Miller returns the largest figure at the 152.4 cm floor and the smallest at 190 cm, while Hamwi does exactly the reverse — the two lines cross somewhere in between. A single number lifted out of this set carries whichever formula's constants you happened to lift, and gives no indication that a selection was made.
The sex switch moves both constants at once, so the shape of the disagreement changes with it too. At 165 cm the male set spans 1.8 kg while the female set at the same height spans 3.4 kg. Same height, a different pair of lines, a differently sized band.
Why the calculator stops at 5 ft
Below 152.4 cm this tool returns no number at all. That boundary belongs to the formulas, not to the calculator: each is defined as a base value at 5 ft plus per-inch increments above it, and below the floor there is no rule left to apply — only a base value with increments subtracted from it. The arithmetic would still produce a figure, since subtracting is a perfectly well-defined operation, and that figure would be an extrapolation past the edge of the definition, printed in the same typeface and to the same decimal place as a value from well inside it. Asked for 150 cm, the engine declines instead, with its own wording: "The classic ideal-weight formulas are defined for heights of 5 ft (152.4 cm) and above."
Refusing is the behaviour that carries information. An extrapolated figure gives no signal that it has left the range where its rule was defined; it looks exactly like every other number on the page. The engine behaves the same way everywhere else on this site — heights outside 50 to 280 cm and weights outside 10 to 500 kg are refused with an explanation rather than answered wrongly. The 152.4 cm floor is simply this calculator's additional constraint on top of the general one.
What is not in any of the four
None of the four consider body composition. There is no term for it because there is no input for it: the whole calculation is a height and a sex. Two people of identical height and sex receive identical output from all four formulas, whatever else differs between them. That is not a limitation the formulas are concealing — it is the full extent of what they were built to do.
Composition is a separate question with separate inputs and a separate error band. The body-fat calculator estimates percent fat from height plus neck and waist girths (and hip, for women) by the US Navy circumference method, and reports a standard error against reference methods such as underwater weighing commonly given as roughly 3–4 percentage points. BMI answers a third question again: it is a screening ratio rather than a body-fat measure, and the guide what BMI does and does not measure sets out the places that ratio is documented to mislead. Longer write-ups of the formulas behind every calculator here live in the guides, and the condensed formula-by-formula reference is on the methodology page.
How to read the spread
The honest output of this page is the band, not a point chosen from inside it. The two useful readings are its position and its width. Position is what the four formulas broadly agree on at that height. Width is how much of the result is being supplied by the choice of formula rather than by the height entered — and, as the table above shows, that width is not constant. Across the heights tabled there it contracts toward the middle and opens out at both ends, which means the same tool is far more decisive at some heights than at others.
Averaging the four would hide exactly that. It would return one number of apparently equal quality at every height, when the agreement between the rules varies by 9.4 kg between the narrowest and widest rows above. Reporting all four keeps the uncertainty visible where it belongs: on the page, rather than folded into a mean.
Every worked figure above — the four formula outputs, the constants table, the spread table and the values drawn from them — is computed at build time by the same functions the form calls in your browser, so the copy and the code cannot drift apart. Nothing you enter into the form is transmitted or stored; the calculation runs locally.
Frequently asked questions
Where do these formulas come from?
All four originated decades ago in clinical contexts; the Devine formula was proposed for drug dosing. Mechanically they share one shape: a base weight at 5 ft (152.4 cm) plus a fixed increment for every inch of height above it, with a different base and increment for each formula and for each sex. This calculator reports all four rather than picking one.
Why do the four formulas disagree?
Each is a straight line with its own starting point and its own slope, so the four cross rather than coincide. They disagree with each other by design, which is why all four are shown. The width of the disagreement changes with height: across the male heights tabled on this page the four land within 1.5 kg of each other at 170 cm and span 10.9 kg at 190 cm.
Which of the four should I use?
The calculator does not choose, and neither does this page. A single figure lifted out of the set would carry a precision the set does not have, and would hide the fact that a choice was made at all. The spread between the four is the output.
Do the formulas account for muscle, frame, or age?
None of them consider body composition, and none of them take any input beyond height and sex. Two people of the same height and same sex receive identical numbers from all four formulas, whatever else is true of them. The body-fat calculator asks a different question, from different inputs, by a different formula.
Why are the male and female results different?
Each formula carries its own base value for each sex, and all but one of the four also change slope. At 165 cm the male set spans 1.8 kg and the female set spans 3.4 kg — the same height run through a different pair of lines.
Is my healthiest weight inside this range?
That is not a question these formulas can answer. They contain no term for body composition and no input for anything except height and sex, so they cannot describe the person the height belongs to. Weight goals belong in a conversation with a qualified healthcare professional who can see your whole picture.
Why is there no result below 5 feet?
The formulas are defined as a base value at 5 ft plus per-inch increments above it, so below 152.4 cm there is no rule left to apply — only the base value with increments subtracted from it. The arithmetic would still return a figure, and that figure would be an extrapolation printed with the same confidence as a value inside the defined range. Asked for 150 cm, the engine declines instead: "The classic ideal-weight formulas are defined for heights of 5 ft (152.4 cm) and above."
Are the worked examples on this page the same ones the calculator produces?
Yes. The four formula outputs, the constants table, the spread table and the figures drawn from them are all computed at build time by the same functions the form calls in your browser, so those examples and the code cannot drift apart. Other figures in the text — the accepted input ranges, and the body-fat error band quoted in passing — are stated values rather than worked examples, and are set out on the methodology page.
Not medical advice: this calculator provides general educational estimates from published population formulas. It cannot account for your individual health context and must not be used to diagnose or treat any condition — consult a qualified healthcare professional. Measurements are processed locally in your browser and never transmitted. See the methodology page.