On this page (11)
How to use this calculator#
- Measure height without shoesHeels together against a wall, looking straight ahead, measured to the crown of the head. Every formula here adds a fixed amount per inch above five feet, so a 2 cm error changes the Devine result by about 1.8 kg.
- Select your sexAll four formulas use different base weights and, in three of the four, different per-inch increments for men and women. There is no single unisex version — the results are not interchangeable.
- Read the four results as a band, not a targetThe formulas will typically fan out by three to four kilograms at the same height. That spread is the honest resolution of the method. Nothing distinguishes the middle of that band as more 'correct' than the edges.
- Compare against the healthy weight range shown alongsideThe BMI-derived 18.5–24.9 range is usually the more useful output because it is a span rather than a point, and it is the figure health services actually use. At most adult heights it is around 20 kg wide.
The formula#
Devine, Robinson, Miller and Hamwi ideal body weight formulas
IBW (kg) = base + increment × (height in inches − 60)
- base
- Weight at exactly 5 ft — Devine 50/45.5, Robinson 52/49, Miller 56.2/53.1, Hamwi 48/45.5 kg (men/women)
- increment
- Kilograms added per inch above 5 ft — Devine 2.3 for both sexes; Robinson 1.9/1.7; Miller 1.41/1.36; Hamwi 2.7/2.2 (men/women)
- height in inches
- Standing height converted to inches: centimetres ÷ 2.54
- 60
- Five feet in inches — the anchor point for every one of these formulas
Devine (1974) was published to standardise drug dosing, not to guide body weight goals, and Hamwi (1964) came from an American Diabetes Association guide to estimating calorie and insulin needs. Robinson (1983) and Miller (1983) were reanalyses of Metropolitan Life insurance height–weight tables drawn from US policyholders. None was validated as a health target for the general population, and all are undefined in behaviour below 5 ft, where the base weight dominates entirely. The tool also reports the healthy weight range as 18.5 × height² to 24.9 × height², with height in metres.
Four formulas, four slightly different answers#
Every formula here starts from a base weight at five feet and adds a fixed amount per inch above that. Devine (1974) starts at 50 kg for men and 45.5 kg for women, adding 2.3 kg per inch. Robinson (1983), Miller (1983) and Hamwi (1964) use different bases and increments, which is why they fan out by several kilograms at the same height.
At 175 cm, a man works out to about 70.5 kg by Devine, 68.9 kg by Robinson, 68.7 kg by Miller and 72.0 kg by Hamwi. The clustering is reassuring, but a spread of more than three kilograms at a single height is a useful reminder that none of these is a precise personal target.
Where these numbers actually came from#
The Devine formula was written to calculate drug dosages, not to guide dieting, and Hamwi came from a 1964 insulin dosing guide for people with diabetes. They persist in clinical software because they are simple and conservative, not because they were validated as health targets for the general public.
That history explains their blind spots. None of them account for frame size, muscle mass, age or ethnicity, and all of them are poorly behaved below about 150 cm, where the base weight dominates. Treat the four results as a rough band rather than a goal weight.
A better framing: the healthy weight range#
The BMI-derived range shown alongside is usually more useful, because it gives a band rather than a single figure. It is the weight that puts you between a BMI of 18.5 and 24.9, so at 175 cm that is roughly 56.7 kg to 76.2 kg, a span wide enough to accommodate very different builds.
Body composition, blood pressure, resting heart rate, waist circumference and how you feel day to day all say more about health than a target weight does. These results are general information and not medical advice. Discuss any significant weight goal with a doctor, particularly if you have a chronic condition or a history of disordered eating.
Worked examples#
Man, 175 cm — all four formulas
Converting height to inches above five feet and applying each formula in turn.
- Height in inches = 175 ÷ 2.54 = 68.90 in, so inches above 60 = 8.90
- Devine: 50 + (2.3 × 8.90) = 50 + 20.47 = 70.5 kg
- Robinson: 52 + (1.9 × 8.90) = 52 + 16.91 = 68.9 kg
- Miller: 56.2 + (1.41 × 8.90) = 56.2 + 12.55 = 68.7 kg
- Hamwi: 48 + (2.7 × 8.90) = 48 + 24.02 = 72.0 kg
- Healthy BMI range: 1.75² = 3.0625, so 18.5 × 3.0625 = 56.7 kg and 24.9 × 3.0625 = 76.3 kg
68.7–72.0 kg across the four formulas, inside a healthy weight range of 56.7–76.3 kg. The formulas cluster near the upper-middle of the BMI band, which is typical for men.
Woman, 163 cm — and why the spread matters
The same arithmetic with the female constants.
- Height in inches = 163 ÷ 2.54 = 64.17 in, so inches above 60 = 4.17
- Devine: 45.5 + (2.3 × 4.17) = 45.5 + 9.60 = 55.1 kg
- Robinson: 49 + (1.7 × 4.17) = 49 + 7.09 = 56.1 kg
- Miller: 53.1 + (1.36 × 4.17) = 53.1 + 5.67 = 58.8 kg
- Hamwi: 45.5 + (2.2 × 4.17) = 45.5 + 9.18 = 54.7 kg
- Healthy BMI range: 1.63² = 2.6569, so 49.1 kg to 66.2 kg
54.7–58.8 kg across the four formulas — a 4.1 kg spread — inside a healthy range of 49.1–66.2 kg that is 17 kg wide. Treating any single one of those four numbers as a goal weight ignores a spread the formulas themselves cannot resolve.
Reference tables#
| Formula | Year | Men | Women |
|---|---|---|---|
| Devine | 1974 | 50 kg + 2.3 kg/inch | 45.5 kg + 2.3 kg/inch |
| Robinson | 1983 | 52 kg + 1.9 kg/inch | 49 kg + 1.7 kg/inch |
| Miller | 1983 | 56.2 kg + 1.41 kg/inch | 53.1 kg + 1.36 kg/inch |
| Hamwi | 1964 | 48 kg + 2.7 kg/inch | 45.5 kg + 2.2 kg/inch |
Hamwi was originally written in imperial units — 106 lb + 6 lb per inch for men, 100 lb + 5 lb per inch for women. The metric constants above are the conventional rounded conversions and differ from an exact conversion by a few tenths of a kilogram.
| Height | Devine — men | Devine — women | Healthy range (BMI 18.5–24.9) |
|---|---|---|---|
| 155 cm / 5 ft 1 in | 52.4 kg | 47.9 kg | 44.4 – 59.8 kg |
| 160 cm / 5 ft 3 in | 56.9 kg | 52.4 kg | 47.4 – 63.7 kg |
| 165 cm / 5 ft 5 in | 61.4 kg | 56.9 kg | 50.4 – 67.8 kg |
| 170 cm / 5 ft 7 in | 65.9 kg | 61.4 kg | 53.5 – 72.0 kg |
| 175 cm / 5 ft 9 in | 70.5 kg | 66.0 kg | 56.7 – 76.3 kg |
| 180 cm / 5 ft 11 in | 75.0 kg | 70.5 kg | 59.9 – 80.7 kg |
| 185 cm / 6 ft 1 in | 79.5 kg | 75.0 kg | 63.3 – 85.2 kg |
| 190 cm / 6 ft 3 in | 84.0 kg | 79.5 kg | 66.8 – 89.9 kg |
Notice that the Devine figure sits in the upper half of the healthy range at every height, and for taller men approaches its top. That is an artefact of a formula built for drug dosing, not a statement that lighter is unhealthy.
Common mistakes#
- Treating an ideal weight figure as a goalNone of these formulas was validated as a health target. Devine exists so clinicians can dose drugs consistently, and Hamwi came from a diabetes management guide. Adopting one as a personal goal weight applies a dosing convention to a question it was never asked.
- Using them on muscular bodiesHeight is the only input. A trained athlete at 175 cm can carry 8–10 kg more lean tissue than the Devine figure and be leaner than average while apparently 'over' their ideal weight. Body fat percentage answers that question; these formulas cannot.
- Applying them below about 150 cmBelow five feet the increment term goes to zero or negative and the base weight dominates, so all four formulas converge on an implausible figure. They are also not valid for children or adolescents, who are assessed on growth charts.
- Ignoring that the source populations were narrowRobinson and Miller were derived from mid-twentieth-century US life insurance tables, which reflected the insured American population of the time. Frame size, ancestry and age are absent from all four equations, and none of them was designed to be applied globally.
Frequently asked questions#
Which ideal weight formula should I use?
Devine and Robinson are the most commonly cited, but the honest answer is to use the healthy BMI range instead. A band accommodates differences in frame and muscle that a single number cannot.
Do these formulas work for athletes?
Not well. They ignore muscle mass entirely, so a lean, muscular person often exceeds every ideal weight figure while carrying very little fat. Body fat percentage is a better measure for them.
Why is there no age input?
None of the four classic formulas include age. They were derived from adult populations and are not appropriate for children or teenagers, whose growth charts are used instead.
Key terms#
- Ideal body weight (IBW)
- A height-derived reference weight from a published formula. In clinical practice it is used mainly to standardise drug dosing and ventilator settings, not as a health goal.
- Healthy weight range
- The weight span corresponding to a BMI of 18.5 to 24.9 at a given height. A band rather than a point, and the reference used by the WHO and national health services.
- Adjusted body weight
- A clinical correction used when actual weight greatly exceeds IBW: usually IBW plus 40% of the difference. It exists because some drugs distribute partly into fat tissue.
- Frame size
- Skeletal build, historically estimated from elbow breadth or wrist circumference. The Metropolitan Life tables that Robinson and Miller drew on adjusted for it; the formulas themselves do not.
- Metropolitan Life tables
- Height–weight tables published by an American life insurer in 1943 and 1983, derived from policyholder mortality data. They are the historical ancestor of much of the ideal weight literature.
- Lean body mass
- Total weight minus fat mass. Two people at the same height and identical 'ideal weight' can differ by 15 kg of lean mass, which is precisely what these formulas cannot see.
Sources#
- Calculate your body mass index — healthy weight ranges by height — NHS
- Obesity and overweight — WHO adult BMI classification — World Health Organization
- BMI table for adults — height and weight reference chart — NIH / NHLBI
- Overweight and obesity — definition and facts — NIH / NIDDK
Figures last checked .
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