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56.4 kg – 59.8 kg
Four published formulas, four different answers. The spread is the honest result.
An estimate, not medical advice, and not a goal handed down by anyone. There is no single ideal weight for a height: the four formulas here disagree by several kilograms at every height, and none of them knows anything about your build, your muscle or your health. Devine’s was written in 1974 to size a gentamicin dose, not to set a target; the others grew out of insurance tables. Read the spread, not any one row.
The four are Devine (1974), Robinson (1983), Miller (1983) and Hamwi (1964), each a base weight at five feet plus a fixed amount per inch above it, and each fitted separately for men and women. The healthy BMI range beside them is the World Health Organization’s, and it is the one based on population health outcomes rather than on dosing convenience — which is why it is a band rather than a point.
If a single correct weight existed for a given height, medicine would have published one equation rather than a dozen. What exists instead is a family of formulas, all built the same way — a base weight at five feet plus a fixed amount for every inch above it — and all disagreeing with each other. This calculator runs four of the best known and reports the spread, because the spread is the honest answer.
Alongside them it shows the weight band that corresponds to a healthy body mass index at the same height. That band is the one derived from population health outcomes rather than from clinical convenience, and it is deliberately wide.
For a man 180 cm tall, Miller returns 71.5 kg, Robinson 72.6 kg, Devine 75.0 kg and Hamwi 77.3 kg. Nearly six kilograms separate the lowest from the highest, and every one of those figures is published and in clinical use. The healthy BMI band for the same height runs from 59.9 kg all the way to 80.7 kg, comfortably containing all four.
For a woman 165 cm tall the four land between 56.4 kg and 59.8 kg, against a healthy band of 50.4 kg to 67.8 kg. The pattern holds at every height: the formulas cluster near the middle of a range that is roughly three times as wide as their disagreement.
Hamwi’s came first, in a 1964 American Diabetes Association handbook, as a bedside method for estimating diet prescriptions. Devine published his in 1974 for a completely different purpose: working out a gentamicin dose, where lean mass matters and total body weight would overdose a heavy patient. It was never proposed as a health target, and it remains the most widely used weight formula in pharmacy for that reason.
Robinson and Miller both published revisions in 1983, refitting the coefficients against the Metropolitan Life insurance tables that dominated the era. Those tables were themselves derived from mortality among people who had bought life insurance, which is not a representative sample of anybody.
For most purposes the BMI band is a better answer than any single formula, precisely because it is a range. Inside it, a waist measurement tells you more than the scale does — abdominal fat tracks metabolic risk in a way that total mass does not.
Two limits are worth knowing. Every one of these formulas was built from adults at or above five feet, so below that the per-inch term simply runs backwards; Hamwi published that downward step, and the other three are extrapolating. And none of them accounts for build, muscle or frame size, so a heavily muscled body will sit above every figure here while carrying very little fat.
None of them individually. They were fitted for different purposes against different data and there is no evidence that any one is closer to a health optimum than the others. Read the spread as a rough neighbourhood, and treat the healthy BMI band as the wider and better-grounded answer.
Because none of the four measures it. Older insurance tables did adjust for small, medium and large frames, usually by elbow breadth or wrist circumference, but the adjustments were never well validated and the formulas that survived dropped them. It is a genuine gap, not an oversight this tool can fill.
Not as a target. Muscle is heavy, and a trained rugby player or rower will exceed every figure here while carrying less fat than most people in the healthy band. Body composition is the measurement that answers the question they are actually asking, not a height-based estimate of mass.
They do not — age appears in none of them. Body composition does change with age, with lean mass falling and fat rising at a stable weight, and there is evidence that a slightly higher weight is protective in older adults. The formulas are blind to all of that.