Where these formulas actually come from
None of the four was designed to tell you what you should weigh. Dr. B.J. Devine published his formula in 1974 so hospital pharmacists could dose drugs like gentamicin, which distribute through lean tissue rather than fat. He needed a quick estimate of lean body size from height, and by his own account picked the constants from earlier rules of thumb rather than from measured data.
The Hamwi rule is older still: G.J. Hamwi published it in a 1964 American Diabetes Association handbook as bedside shorthand for setting diet plans. Robinson and Miller each published corrections to Devine in 1983 after checking his numbers against insurance height-and-weight tables and finding them off at the extremes, Robinson adjusting down for tall men, Miller flattening the slope further.
So the honest summary is: one dosing tool, one diabetes-clinic shorthand, and two corrections to the dosing tool. Useful history, thin evidence for setting a personal goal. Worth keeping in mind before treating any of the outputs as a verdict on your body.
The four formulas
| Formula | Men | Women |
|---|---|---|
| Devine (1974) | 50 kg + 2.3 kg per inch over 5 ft | 45.5 kg + 2.3 kg per inch over 5 ft |
| Robinson (1983) | 52 kg + 1.9 kg per inch over 5 ft | 49 kg + 1.7 kg per inch over 5 ft |
| Miller (1983) | 56.2 kg + 1.41 kg per inch over 5 ft | 53.1 kg + 1.36 kg per inch over 5 ft |
| Hamwi (1964) | 48 kg + 2.7 kg per inch over 5 ft | 45.5 kg + 2.2 kg per inch over 5 ft |
Why the numbers disagree
Each author picked a different starting weight at 5 ft and a different amount per inch, so the formulas fan out as height rises. For a 5'10" man the spread runs from 70.3 kg (Miller) to 75 kg (Hamwi), about 10 lb of disagreement. For a 5'4" woman it runs from 54.3 to 58.5 kg. There is no experiment that settles which is right, because they were never measuring the same thing.
Compare that with the range built from the BMI evidence. At 5'10", a BMI of 18.5–24.9 covers roughly 58.5 to 78.7 kg. All four ideal-weight results sit comfortably inside it, which tells you something useful: the formulas are four arbitrary points within a wide healthy band, not four attempts at one true number.
What to do with the number
Treat the output as a landmark, not a destination. If your weight is far above or below all four estimates, that is worth noticing, in the same way an unusual BMI is worth noticing. If you sit within a few kilograms of them, the formulas have nothing more to tell you.
A goal weight you can actually hold matters more than a formula-perfect one. Pick a number inside the healthy BMI band that fits your build and training history, then work out the calories that get you there: the TDEE calculator finds your maintenance level, and a 250–500 calorie daily adjustment moves you roughly 0.25–0.5 kg per week. People who carry a lot of muscle should lean on a body fat estimate instead; for them, height-only formulas miss the most important variable entirely.
