Why seven formulas, not one number
Type your height into most “ideal body weight” (IBW) calculators and you get a single confident figure. That confidence is false. The published formulas — Devine, Robinson, Miller, Hamwi, Broca, Lorentz, Peterson — disagree by several kilograms for the same person, because each was built on a different population, decade and purpose. We show all of them and the spread between them, because the spread is the honest answer: there is no single ideal weight.
Where these formulas actually came from
Almost none was designed to tell an individual what to weigh. Devine (1974) was a rule for calculating drug doses. Robinson and Miller (1983) are regressions on mid-century life-insurance tables. Hamwi (1964) was a bedside shortcut for clinicians. Broca (1871) and Lorentz (~1929) are old anthropometric indices. Reading them as a personal health goal asks them to do a job they were never built for.
A measure that rests on data
If you want a number anchored to health outcomes rather than insurance actuaries, a BMI healthy-weight range (18.5–24.9 × your height²) or your waist-to-height ratio says more — and both describe your body rather than prescribing it. Try waist-to-height ratio →
FAQ
Is there a single ideal weight?
No — and that’s the honest answer this page is built around. The historical formulas disagree by several kilograms for the same height, because each was built on a different population and for a different purpose. We show the spread instead of picking one number, because there is no single ideal weight to pick.
Where do ideal-weight formulas come from?
Most come from the mid-20th century. Devine (1974) was a rule for drug dosing; Robinson and Miller (1983) were regressions on Metropolitan Life insurance tables; Hamwi (1964) was a clinical bedside shortcut; Broca (1871) and Lorentz (~1929) are old anthropometric indices. None was designed as a personal health goal.
Which ideal-weight formula is most accurate?
None is “accurate”, because ideal weight isn’t a measurable quantity — it’s a definition, and the formulas define it differently. They’re useful for showing how much the idea of a “normal” weight has varied, not for setting a target. For something anchored to health data, a BMI healthy-weight range or waist-to-height ratio is more honest.
Should I try to reach my ideal weight?
We’d gently push back on the framing. These numbers aren’t goals, and health isn’t a single figure on a chart. If you want measures that rest on data rather than mid-century tables, waist-to-height ratio and a body-fat estimate say more — and they describe your body, they don’t prescribe it.
How much should I weigh for my height and age?
Honestly, there isn’t one right number. The historical formulas here use only your height — none factors in age — and they still disagree by several kilograms for the same person. For adults, a healthy weight isn’t set by age either: the data-backed answer is the BMI healthy-weight range for your height (18.5–24.9 × your height in metres squared), which is a wide band, not a point, with waist-to-height ratio as a second body-shape check. Those rest on health data, unlike a mid-century formula telling you what you “should” weigh.
What is a healthy weight range for my height?
A range from BMI 18.5–24.9 times your height in metres squared gives a population-level healthy-weight band — and notice it’s a wide range, not a point. It rests on health data, unlike the historical ideal-weight formulas, which is why we show it as the contrast.