Ideal Weight Calculator
Compare ideal body weight from the Hamwi, Devine, Robinson and Miller formulas with the BMI 18.5 to 24.9 weight range for your height and sex.
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About this toolWhat is the Ideal Weight Calculator?
The Ideal Weight Calculator answers "what should I weigh for my height?" four ways at once. Enter your height and sex and the page lists the result from each of the classic ideal body weight (IBW) formulas: Hamwi (1964), Devine (1974), Robinson (1983) and Miller (1983). Beside them it shows the weight range that keeps your BMI between 18.5 and 24.9, the World Health Organization healthy band for adults.
The formulas rarely agree. For a 165 cm woman they run from 56.6 to 59.8 kg, while the BMI band runs from 50.4 to 67.8 kg. That spread is the honest answer: there is no single ideal number, only a range where health risks are low for most people. If you add your current weight, a marker shows where you sit against both ranges.
Calculations happen in your browser and update as you type. Nothing is stored.
- Hamwi, Devine, Robinson and Miller side by side
- Healthy BMI 18.5 to 24.9 weight range for your height
- Optional current weight with BMI and a visual marker
- Metric or feet and inches, kg or lb
- Explains the formula constants and why they differ
How to use the Ideal Weight Calculator
- Select Female or Male. The formulas use different constants for each.
- Choose Metric and type your height in centimetres, or US and type feet and inches.
- Optionally enter your current weight to see your BMI and a marker on the comparison bar.
- Read the formula range, the average of the four, and the healthy BMI weight range.
- Open the explanation to see why the formulas disagree at your height, or copy a summary to share.
Worked examples
Woman, 165 cm
Input
Female, 165 cm
Output
Hamwi 56.6 kg, Devine 56.9 kg, Robinson 57.4 kg, Miller 59.8 kg; BMI range 50.4 to 67.8 kg
She is 4.96 inches over 5 ft. The four formulas sit within 3.2 kg of each other, all near the middle of the much wider BMI band.
Man, 5 ft 10 in
Input
Male, 5 ft 10 in
Output
Hamwi 75.3 kg (166 lb), Devine 73.0 kg, Robinson 71.0 kg, Miller 70.3 kg; BMI range 58.5 to 78.7 kg
Hamwi is the most generous for taller men because its 6 lb (2.72 kg) per inch is the steepest slope. Miller is the lowest at this height.
Short stature
Input
Female, 150 cm
Output
Hamwi 43.2 kg, Devine 43.3 kg, Robinson 47.4 kg, Miller 51.8 kg (extrapolated)
Below 5 ft the formulas are being run backwards past their design range, and Miller ends up 8.6 kg above Hamwi. The page flags this; the BMI range of 41.6 to 56.0 kg is the better guide here.
Background and insight
All four formulas share one shape: a base weight at 5 feet (152.4 cm) plus a fixed amount for each extra inch. Hamwi gave dietitians a bedside rule of 106 lb plus 6 lb per inch for men and 100 lb plus 5 lb per inch for women. Devine published 50 kg plus 2.3 kg per inch (men) and 45.5 kg plus 2.3 kg per inch (women) in 1974 as a way to dose the antibiotic gentamicin, and pharmacists still use it to calculate drug doses and ventilator settings.
In 1983 Robinson and colleagues, and separately Miller and colleagues, refitted the same straight-line shape to the Metropolitan Life Insurance height-weight tables. Robinson uses 52 kg plus 1.9 kg per inch for men and 49 kg plus 1.7 kg for women; Miller uses 56.2 kg plus 1.41 kg and 53.1 kg plus 1.36 kg. The gentler slopes mean Miller gives the highest result for short people and one of the lowest for tall people. For men the lines cross between about 5 ft 5 in and 5 ft 9 in; for women, between about 5 ft 7 in and 6 ft 1 in.
None of these equations was derived from health outcomes, and none considers frame size, muscle, age or ethnicity. The BMI band does come from outcome data, though it has its own blind spots. This page treats the formulas as reference points and the BMI range as the wider target.
Common use cases
Setting a realistic goal weight
See a band rather than a single number before choosing a target for a diet plan.
Drug dosing reference
Check the Devine IBW that pharmacists use for aminoglycosides, ventilator tidal volume and creatinine clearance estimates.
Comparing advice from different sources
Understand why one website says 57 kg and another says 60 kg for the same height.
Talking to a teenager or older relative
Show that "ideal" is a range and that the formulas were never meant as personal targets.
Tips and limitations
- Use the BMI range as the main target and the formula numbers as reference points within it.
- If you are muscular, expect to sit above every formula result while still being lean. A body fat or waist measurement is the better check.
- Heights below 5 ft are outside the formulas' design. The page extends them with the same slope and marks the result as extrapolated.
- For drug dosing, clinicians often switch between actual, ideal and adjusted body weight depending on the drug. Follow your pharmacist, not this page.
- Older adults tend to have better outcomes at the upper half of the BMI range, so a lower formula weight is not automatically better after about 65.
Frequently asked questions
Which ideal weight formula is the most accurate?
None of them is accurate in the sense of predicting the healthiest weight for you, because none was built from health outcomes. Devine is the clinical standard for drug dosing. Robinson and Miller fit the 1983 insurance tables more closely. The BMI range is the better guide for health.
What is the Devine formula?
Men: 50 kg plus 2.3 kg for every inch over 5 feet. Women: 45.5 kg plus 2.3 kg per inch. A 6 ft man gets 50 + 2.3 × 12 = 77.6 kg. It dates from a 1974 paper on gentamicin dosing.
How much should I weigh for my height?
For adults, a weight that keeps BMI between 18.5 and 24.9 is the usual answer. At 175 cm that is about 56.7 to 76.3 kg. Where you sit in that band depends on muscle, frame and age.
Why do ideal weight calculators give different answers?
Each formula uses its own base weight at 5 ft and its own increment per inch. Steeper formulas such as Hamwi and Devine give more weight to tall people, and flatter ones such as Miller give more to short people. For men the four lines cross between about 5 ft 5 in and 5 ft 9 in, so the order flips around average height.
Does frame size change my ideal weight?
Hamwi suggested adding 10% for a large frame and subtracting 10% for a small frame, usually judged by wrist circumference. The other formulas ignore frame. This page does not apply a frame adjustment, so allow a few kilograms either way.
Is ideal body weight the same as healthy weight?
No. Ideal body weight is a formula output used mostly for dosing and nutrition planning. A healthy weight is a range where disease risk is low, which the BMI band approximates. Plenty of healthy people weigh more than every formula result.
Is there an in-depth guide to the Ideal Weight Calculator?
Yes. “Body Fat, Ideal Weight and Macros: What the Formulas Can and Cannot Tell You” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
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