Ideal Weight Calculator (Devine, Robinson, Miller, Hamwi)
Ideal body weight by the four clinical formulas — Devine, Robinson, Miller and Hamwi — side by side, with the BMI 18.5–24.9 healthy range for your height.
Inputs
| Formula | Men | Ideal weight |
|---|---|---|
| Devine (1974) | 50 kg + 2.3 kg/in | 65.9 kg |
| Robinson (1983) | 52 kg + 1.9 kg/in | 65.2 kg |
| Miller (1983) | 56.2 kg + 1.41 kg/in | 66.0 kg |
| Hamwi (1964) | 106 lb + 6 lb/in | 66.9 kg |
- Formula
- Devine (1974)
- Height over 5 ft
- 6.9 in (66.9 in tall)
- Working
- 50 kg + 2.3 kg × 6.9 in = 65.9 kg
- Spread across all four formulas
- 65.2 kg – 66.9 kg
- Healthy weight for your height (BMI 18.5–24.9)
- 53.5 kg – 72.0 kg
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What each Ideal Weight input means
- Height
- Height without shoes. Every formula counts inches over 5 feet (152.4 cm), so heights below that are outside what they were built for.
- Sex
- The formulas use a different starting weight for men and women, and Robinson, Miller and Hamwi a different amount per inch too.
- Formula
- Devine is the clinical default for drug dosing. Robinson and Miller are refits to insurance tables; Hamwi is the older pounds-based rule. All four are shown in the table whichever you pick.
Ideal Weight formula
Ideal weight = base weight at 5 ft + a fixed amount per inch over 5 ft · Devine: men 50 kg + 2.3 kg/in, women 45.5 kg + 2.3 kg/in
The 'ideal body weight' formulas all have the same shape: a starting weight for someone exactly 5 feet tall, plus a fixed amount for every inch above that. Ben Devine published his in 1974 to dose the antibiotic gentamicin, and it is still the one hospitals use for drug doses; Robinson and Miller fitted their versions in 1983 to the Metropolitan Life insurance height-weight tables, and Hamwi's 1964 rule of thumb was stated in pounds. Pai and Paloucek's review in 2000 traced them back and found they agree because the tables they came from agree. The page gives the formula you choose as the headline, shows all four in a table, and adds the weight range that keeps BMI between 18.5 and 24.9 — the CDC's healthy band — since that is the usual answer to 'what should I weigh'. The formulas give one number; the BMI band gives a range that is wide for a reason, because frame and muscle differ.
Ideal Weight worked example
A man 170 cm tall is 66.9 inches, 6.9 inches over 5 feet. Devine gives 50 + 2.3 × 6.9 = 65.9 kg. The four formulas span 65.2 kg (Robinson) to 66.9 kg (Hamwi), so they barely disagree at this height. The BMI healthy range for 170 cm is far wider: 53.5 to 72.0 kg.
More Ideal Weight examples
A woman 5 ft 4 in tall, 4 inches over 5 feet. Robinson gives 49 + 1.7 × 4 = 55.8 kg, which is 123.0 lb. Devine says 120.6 lb, Miller 129.1 lb and Hamwi 100 + 5 × 4 = 120.0 lb; the BMI healthy band for her height runs from 107.8 to 145.1 lb.
A man 5 ft 10 in tall by Hamwi's rule: 106 lb for the first 5 feet plus 6 lb for each of the 10 inches above, 106 + 60 = 166.0 lb.
Where the Ideal Weight calculator can give the wrong answer
- These are not health targets. Devine's formula was written for medication dosing, and none of the four was tested against health outcomes; a muscular person can sit well above every one of them and be perfectly healthy.
- Below 5 ft the inch term turns negative and the formulas subtract weight from their base. They were not designed for those heights, so the page warns and the BMI range is the better guide.
- The formulas grow apart with height. At 5 ft 7 in they agree within 2 kg; at 6 ft 6 in Miller and Hamwi differ by more than 30 lb, because their per-inch rates differ.
- Hamwi was published in pounds and is kept in pounds here. Many sites use a rounded metric version (48 kg + 2.7 kg per inch), which gives a slightly different answer.
- None of the formulas use age, frame size or body composition. The BMI band at least admits a range; read the single number as the middle of one.
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Ideal Weight reference table
| Formula | Men | Women |
|---|---|---|
| Devine (1974) | 50 kg + 2.3 kg per inch over 5 ft | 45.5 kg + 2.3 kg per inch |
| Robinson (1983) | 52 kg + 1.9 kg per inch | 49 kg + 1.7 kg per inch |
| Miller (1983) | 56.2 kg + 1.41 kg per inch | 53.1 kg + 1.36 kg per inch |
| Hamwi (1964) | 106 lb + 6 lb per inch | 100 lb + 5 lb per inch |
Ideal Weight FAQ
- Start from a base weight at 5 feet and add a fixed amount per inch above that. Devine: 50 kg for men or 45.5 kg for women, plus 2.3 kg per inch. A 5 ft 8 in man: 50 + 2.3 × 8 = 68.4 kg (150.8 lb).
- By the formulas, a single figure — 65.9 kg for a 170 cm man by Devine, 123 lb for a 5 ft 4 in woman by Robinson. By BMI, a range: the weights that put BMI between 18.5 and 24.9. The range is the better target for most people; the page shows both.
- None is accurate for an individual; they are averages from insurance tables. Devine is the most used, because hospitals dose drugs such as gentamicin with it. Robinson and Miller usually come out a little lower for tall men and higher for short women.
- The formulas add weight in a straight line per inch, while BMI scales with height squared. For tall people the BMI range moves up faster than the formulas, and for short people slower, so the two drift apart at the extremes of height.
- Yes, mainly for dosing drugs that do not spread into fat, for setting ventilator volumes, and for kidney-function formulas. That is the job Devine wrote it for. It is a reference weight for those calculations, not a weight anyone is expected to reach.