How Ideal Weight Formulas Work

The idea of an ideal body weight originated in medicine, not fitness. Physicians needed a quick way to estimate an appropriate weight for a patient of a given height, often to calculate medication doses that depend on body size. That clinical origin is why several competing formulas exist, each proposed by a different researcher.

These formulas take height and biological sex as inputs and return a single target weight. They are deliberately simple, which makes them fast but also means they ignore individual differences in muscle mass, frame size, and body composition.

The Devine formula, published in 1974, is the most widely used, especially for drug dosing. It sets a base weight at a height of five feet and adds a fixed amount per inch above that. The Robinson formula from 1983 and the Miller formula from 1983 are refinements that adjust those base numbers and per-inch increments, generally producing slightly different estimates.

The Hamwi formula, developed in 1964, is the oldest of the four and is popular for quick bedside estimates. Each formula uses a different base and increment for men and women, which is why the same person can get four different target weights. None is definitively correct; they simply reflect different reference populations and assumptions.

The Ideal Weight Calculator runs all four formulas at once and also shows the weight range that corresponds to a healthy BMI for your height, so you can see how the estimates compare. It works entirely in your browser, and none of your inputs are uploaded.

Because the four formulas disagree and none accounts for muscle or frame, the most useful takeaway is a range rather than one figure. Comparing the formula outputs with the healthy BMI range for your height gives you a sensible band to aim for instead of an arbitrary exact weight.

A very muscular person may sit above these estimates while remaining perfectly healthy, and a person with a small frame may feel best near the lower end. The numbers are a starting reference, not a verdict.

Ideal weight figures are estimates and are not a diagnosis or a personalized health plan. They do not measure body fat, fitness, or overall health, and they were never designed to. Use them for rough orientation only.

Before setting a weight goal or making significant changes to diet or exercise, talk with a doctor or a registered dietitian who can account for your full health picture. For a fuller view of your body composition and energy needs, pair these numbers with a body fat estimate and a calorie calculation rather than relying on any single figure.