About the Ideal Weight Calculator
A free tool that shows classic ideal body weight formula estimates and the BMI healthy range side by side — as a spread to compare, not a single number to chase.
What it is
The Ideal Weight Calculator takes your height and sex and shows what four well-known formulas — Devine, Robinson, Miller, and Hamwi — each compute as an ideal body weight, alongside the healthy-weight range derived from the BMI standard (18.5–24.9 × height²). All five results appear at once so you can see the spread immediately.
The tool never presents a single "your ideal weight is X" answer. That framing would misrepresent both the science and the purpose of these formulas. Instead it emphasises the range across methods and the disagreement between them as the honest take-away. Everything runs in your browser — no data is stored or sent anywhere.
Key features
Four classic formulas side by side
Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964) are computed simultaneously for your height and sex, each shown in its own card with a brief note on its origin so you understand the context behind the number.
BMI healthy weight range
Alongside the formula estimates, the tool shows the low end (BMI 18.5) and high end (BMI 24.9) of the standard healthy weight range for your height — a fifth reference that doesn't require a sex input.
Overall spread indicator
A summary row shows the full spread from the lowest to the highest value across all methods, making the disagreement between formulas immediately visible rather than buried in individual cards.
Metric and imperial
Enter height in centimetres or feet and inches; choose output in kg or lb. The tool converts automatically and all formulas produce the same results regardless of which unit system you choose.
The formulas
Devine (1974)
Male: 50 + 2.3 × (inches above 60). Female: 45.5 + 2.3 × (inches above 60). Originally designed to estimate drug dosing weights in clinical pharmacology, not as a personal health target.
Robinson (1983)
Male: 52 + 1.9 × (inches above 60). Female: 49 + 1.7 × (inches above 60). A modification of the Devine formula with slightly different coefficients derived from a re-analysis of population data.
Miller (1983)
Male: 56.2 + 1.41 × (inches above 60). Female: 53.1 + 1.36 × (inches above 60). Tends to produce somewhat higher estimates than Devine and Robinson; developed from a different population sample.
Hamwi (1964)
Male: 48 + 2.7 × (inches above 60). Female: 45 + 2.2 × (inches above 60). One of the oldest clinical rules of thumb, originally described for use in nutritional assessment of diabetic patients.
All four formulas are defined for heights above 5 ft / 152 cm (60 inches). For shorter heights they produce implausible or negative values, so the tool notes this rather than displaying a meaningless result.
Why these formulas have real limits
No body composition
A 175 cm athlete with 10% body fat and a 175 cm sedentary person with 35% body fat receive identical formula results. Muscle and fat are invisible to these equations.
No frame or build
Frame size — small, medium, large — is not accounted for. Two people of the same height but meaningfully different bone structure will naturally carry different healthy weights.
No age factor
Healthy body composition shifts with age. These formulas produce the same output regardless of whether you are 25 or 75, which limits their clinical relevance outside a narrow demographic.
Formulas disagree
For a 5'10" male the four formulas produce a spread of several kilograms. This disagreement itself tells you something important: there is no single "correct" answer hidden in one of them.
This tool is a general reference and is not medical or dietary advice. "Ideal weight" is not a fixed target — formula estimates vary, and none accounts for body composition, muscle mass, frame size, age, or individual differences. Please consult a registered dietitian or physician before making any decisions about your weight or health. If you find yourself preoccupied with your weight or body, consider reaching out to a qualified professional for support.
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