How this works
There's no single "ideal weight" — there are four widely-used clinical formulas, all derived in the 1960s-1980s for drug-dosing in adults. Each takes a base weight at 5 feet (60 inches) of height and adds a per-inch increment for additional height. Results typically agree within ~5 kg, with Miller giving the lightest and Hamwi the heaviest. They're medication-dosing references, not aesthetic targets — for body-composition planning, BMI 18.5-24.9 covers a healthy range and the Body Fat calculator gives a more direct read.
The formula
All four formulas anchor at 5 feet (60 inches) and scale linearly with each additional inch. The 60-inch anchor is itself an artefact: the formulas were derived on US clinical populations using inches, and the constants don't round any cleaner if you re-derive them in centimetres. Below 5 feet the height delta goes negative — so the formulas predict less weight rather than crash, which matters for paediatric or short-stature dosing.
Example calculation
- A man, 178 cm = 70 in tall.
- h − 60 = 10. Devine: 50 + 2.3 × 10 = 73 kg. Robinson: 52 + 1.9 × 10 = 71 kg.
- Miller: 56.2 + 1.41 × 10 ≈ 70.3 kg. Hamwi: 48 + 2.7 × 10 = 75 kg.
- Average ≈ 72.3 kg — a ~5 kg spread between the lowest (Miller) and highest (Hamwi) formula.
Frequently asked questions
Which of the four formulas should I trust?
Use the average. Each formula has minor blind spots — Hamwi tends high for tall people, Miller tends low — so the average smooths out the disagreement and stays within a few kg of any individual formula. For drug dosing, hospital protocols usually pick one specific formula (most commonly Devine) so results are reproducible across staff; if a doctor asks for an exact figure they'll specify which.
Should I aim for my "ideal weight" as a target?
Probably not for body-composition goals. These formulas were designed for drug dosing — they don't account for muscle mass, frame size, or fat distribution. A 90 kg male rugby player at 178 cm is well above the formula's 73 kg, but his body fat % might be 12 % and he's clearly healthy. For body planning, BMI gives a more meaningful range (18.5–24.9 covers "healthy" for most adults), and the Body Fat calculator gives a more direct read on composition.
Why does the formula switch on sex?
Average lean mass differs at the same height. The original studies derived male and female coefficients from gendered clinical populations, and the result is that for the same height women's ideal weight comes out a few kg lower across all four formulas. The size of the gender gap also varies between formulas — Robinson gives the largest gap, Devine has the same per-inch slope for both. Modern guidelines on intersex or transgender dosing recommend using the patient's actual lean body mass via DEXA when precision matters.