Ideal Weight Calculator
Estimate ideal body weight from height and sex using the classic clinical formulas, with a frank explanation of where those formulas came from.
Devine formula · healthy BMI 18.5–24.9
The formula stops working below five feet
Devine is 50 kg plus 2.3 kg for every inch over 60, and "over 60" is clamped at zero. Below five feet there is nothing left to subtract, so the answer freezes: a man of 4'0" and a man of 4'11" are both given exactly 50 kg.
| Height | Devine | Healthy band | Position in the band |
|---|---|---|---|
| 4'0" | 50.0 kg | 27.5–37.0 kg | above the band |
| 4'6" | 50.0 kg | 34.8–46.8 kg | above the band |
| 5'0" | 50.0 kg | 43.0–57.8 kg | 47% |
| 5'4" | 59.2 kg | 48.9–65.8 kg | 61% |
| 5'8" | 68.4 kg | 55.2–74.3 kg | 69% |
| 6'0" | 77.6 kg | 61.9–83.3 kg | 73% |
| 6'4" | 86.8 kg | 68.9–92.8 kg | 75% |
| 6'8" | 96.0 kg | 76.4–102.8 kg | 74% |
Worse than flat: below 55 inches the frozen figure sits above the top of the healthy band for that height, so the formula recommends a weight the range printed beside it would call overweight. Above the clamp every inch is worth exactly 2.3 kg, without exception. If you are under five feet, the band is the number to read and the single figure is not telling you anything.
And it is not a constant target either
Devine is linear in height and BMI is quadratic, so the two cannot track each other. The BMI the formula implies climbs from 21.5 at 5'0" to 23.3 at 6'8" — 1.7 points of drift across the range. The position within the healthy band moves with it, from 47% at 5'0" to 73% at 6'0". A tall person following Devine is aiming much nearer the top of the healthy range than a short person following the same formula.
It does not climb forever, either. A linear numerator over a quadratic denominator has to turn over, and this one peaks at exactly 176/2.3 = 76.52 inches — six foot four and a half — then declines. Anybody taller than that is being aimed slightly lower again, which nothing in the formula announces. To be fair to it, every figure from five feet upward does land inside the healthy band. It is a defensible point inside a wide range, not a wrong answer.
Which is the thing worth taking away: at 5'8" the healthy band is 19 kg wide, and it widens with height because it is quadratic. No single number can express a spread that large — the same height supports very different weights depending on frame and muscle. The male and female versions differ by a flat 4.5 kg at every height, incidentally, which is a shrinking share of the total as you get taller. All of this makes more sense once you know the formula was published in 1974 for estimating drug doses. It needed to be quick, conservative and computable at a bedside, and it is all three. It was never derived from outcome data and was never meant to tell anybody what to weigh.
How to use
- Enter your height and sex.
- Read the estimates from several formulas.
- Read the healthy range rather than fixating on one number.
- Treat the result as context, not a target.
Frequently asked questions
Where do these formulas come from?
Mostly from mid-twentieth-century clinical practice. The Devine formula, still the most widely used, was published in 1974 for calculating drug dosages — not for setting weight goals — and was not derived from health outcome data at all. Robinson, Miller and Hamwi are similar in origin.
Is there really one ideal weight for a given height?
No. Healthy weight is a range rather than a point, and it varies with frame size, muscle mass, body composition, age and ancestry. Any formula returning a single number for everyone of a given height is offering more precision than the underlying science supports.
Why do the formulas disagree with each other?
Because they were fitted to different populations for different purposes, decades apart. A spread of several kilograms between them is normal, and that spread is itself informative — it shows the width of the uncertainty rather than a failure of one formula.
Should I aim for this number?
Not as a target in itself. Health outcomes track body composition, fitness, blood markers and waist circumference far more closely than they track total weight. Someone well outside their calculated ideal weight may be perfectly healthy, and someone within it may not be.
What about athletes?
The formulas fail badly. Muscle is denser than fat, so a well-trained person frequently weighs well above any ideal weight calculation while carrying little fat. This is the same limitation BMI has, from the same cause.
What is a more useful measure?
Waist-to-height ratio is simple and correlates better with health risk than weight alone — keeping waist circumference under half your height is a common rule of thumb. For anything consequential, a clinician's assessment beats any formula. Nothing here is medical advice.
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