Healthy Weight Range Calculator Based on WHO BMI Bands for Your Height

Enter your height. The calculator returns the World Health Organization healthy BMI band of 18.5-24.9 kg/m² applied to your height, shown as a weight range in kilograms, pounds, and stones. That is the headline answer. The Devine, Robinson, Miller, and Hamwi equations below produce different numbers for the same height because they were built for purposes other than defining health. The calculator does not set a target; it reports a screening band.

The Devine, Robinson, Miller, and Hamwi equations are often called ideal body weight formulas, but their original purpose was not to define health. The Devine equation was published in 1974 for calculating initial doses of gentamicin and other aminoglycoside antibiotics in adult medical patients. It was derived from the Metropolitan Life Insurance Company height-weight tables, which were based on policyholders of 26 life insurance companies in the United States and Canada between 1935 and 1953. That sample was not representative of the general population: it was insured, predominantly white, and middle-class. Heights were measured in shoes with approximately 1-inch heels. Weights were recorded in indoor clothing, not nude.

Robinson and Miller Equations (1983)

Both the Robinson and Miller equations appeared in 1983. Each was derived from the Metropolitan Life Insurance Company 1959 desirable weight tables. Like the Devine equation, their original purpose was estimating ideal body weight for pharmacokinetic dosing. The Robinson equation for men is 52 kg plus 1.9 kg per inch over 5 feet; for women, 49 kg plus 1.7 kg per inch. The Miller equation for men is 56.2 kg plus 1.41 kg per inch over 5 feet; for women, 53.1 kg plus 1.36 kg per inch. Notice the equations disagree with each other for the same height. They were modifications of the same insurance-company data, not independent validations against a health outcome.

Hamwi Equation (1964)

The Hamwi equation dates to 1964 and was derived from the same 1959 Metropolitan Life tables. Its original purpose was estimating ideal body weight for clinical nutrition and diabetes management. The Hamwi equation for men is 48.0 kg plus 2.7 kg per inch over 5 feet; for women, 45.5 kg plus 2.2 kg per inch over 5 feet. It also includes a frame-size adjustment: add 10% for large frame, subtract 10% for small frame, with frame size determined by elbow breadth. Elbow breadth has poor inter-rater reliability, and the frame-size cut-offs vary by source. No objective definition existed in the original tables.

The four equations produce divergent ideal weights for the same height because they are distinct mathematical recastings of the same insurance-company data. The Metropolitan Life tables themselves had limitations: mortality follow-up was incomplete for some policyholders, the sample was not representative of the general population, and the frame size categories were not objectively defined. Devine, Robinson, Miller, and Hamwi each picked a different point on that data distribution and called it ideal. None of them was validated against a direct measure of body composition such as DXA or hydrostatic weighing. None accounts for age, ethnicity, or sex differences in body composition.

The WHO healthy BMI band of 18.5-24.9 kg/m² comes from a separate source: epidemiology. It is based on the observed relationship between BMI and disease risk across populations, not on an insurance company's policyholder mortality. The WHO band is a screening tool for population-level risk. The equations were designed for drug dosing and clinical nutrition. The two approaches answer different questions, so they produce different numbers.

None of these equations measures body composition. They cannot distinguish lean mass from fat mass. A muscular individual and an individual with excess body fat at the same height and same equation-calculated weight would look different and carry different metabolic risk. The equations also do not account for waist circumference or waist-to-height ratio, both of which are markers of central adiposity that add information beyond weight.

NICE CG189 (2022) advises keeping waist-to-height ratio below 0.5 as a population-level health signal. That is a heuristic, not a personalised risk score. The Devine equation was written for drug dosing, not for defining health or a target weight. Robinson, Miller, and Hamwi follow the same pattern: they are pharmacokinetic or clinical-nutrition tools, not health benchmarks.

A reader types their numbers into an ideal weight calculator and gets a single number from the Devine or Hamwi equation, then treats that number as a personal health verdict. That number came from a 1974 drug-dosing equation built on an insured population from the 1930s to the 1950s. It was never meant to be a health target. The WHO healthy BMI band is also not a personal health verdict; it is a population screening band. Neither the equations nor the BMI band can tell you your body composition, your waist-to-height ratio, or your individual metabolic risk. No single number from any of these equations or bands can tell you whether you are healthy. That question requires a medical consultation that includes body composition, waist circumference, and a broader set of clinical markers.