Ideal body weight formula: Devine, Robinson, Miller and Hamwi
The four classic ideal body weight formulas with worked examples, where they came from, why they disagree, and how they compare with a healthy BMI range.
The most widely used ideal body weight formula is the Devine formula: 50 kg + 2.3 kg for every inch over 5 feet for men, and 45.5 kg + 2.3 kg per inch over 5 feet for women. For a man who is 5 ft 10 in, that’s 50 + 2.3 × 10 = 73 kg (about 161 lb). This guide sets out the four classic ideal body weight formulas (Devine, Robinson, Miller and Hamwi), works through examples, explains why they were created and why they disagree, and compares them with the healthy BMI range that most health services use today. For your own healthy range, the BMI calculator shows it instantly.
Key takeaways
- Devine (1974): men 50 kg + 2.3 kg/inch over 5 ft; women 45.5 kg + 2.3 kg/inch.
- Robinson and Miller (1983) are later adjustments; Hamwi (1964) is the oldest.
- The formulas were designed for medicine, especially drug dosing, not as personal weight targets.
- They give one number; a healthy BMI range (18.5–24.9) gives a range, which better reflects real bodies.
- None accounts for muscle, frame size, age or ethnicity.
What “ideal body weight” means
“Ideal body weight” (IBW) sounds like a personal goal, but the term comes from clinical medicine. In 1974 the pharmacist Ben J. Devine introduced his formula to help estimate how quickly the body clears certain drugs in patients with obesity; researchers later showed that the handling of some medicines relates more closely to IBW than to total body weight (Wikipedia, Ideal body weight). It’s still used that way today, for example to estimate kidney function for drug dosing and to set ventilator volumes.
Over time the same formulas spread into fitness apps and online calculators as a “weight you should be”. They can be a useful reference, but they were never designed to describe the healthiest weight for an individual. Health services such as the NHS and the WHO use BMI ranges instead, and we’ll compare the two below.
The Devine formula
- Men: IBW = 50 kg + 2.3 kg × (height in inches − 60)
- Women: IBW = 45.5 kg + 2.3 kg × (height in inches − 60)
The formula starts with a base weight for someone exactly 5 feet (60 inches) tall and adds 2.3 kg for each inch above that.
Example: man, 5 ft 10 in
- Height in inches: 5 × 12 + 10 = 70.
- Inches over 5 feet: 70 − 60 = 10.
- IBW = 50 + 2.3 × 10 = 73 kg (about 161 lb).
Example: woman, 5 ft 5 in
- Height: 65 inches, so 5 inches over 5 feet.
- IBW = 45.5 + 2.3 × 5 = 57 kg (about 126 lb).
Wikipedia gives an equivalent version per centimetre: 50 kg (men) or 45.5 kg (women) + 0.9 kg for each centimetre over 152 cm. Because 2.3 ÷ 2.54 ≈ 0.91, the two give almost identical answers.
Robinson, Miller and Hamwi formulas
| Formula | Year | Men | Women |
|---|---|---|---|
| Hamwi | 1964 | 48 kg + 2.7 kg per inch over 5 ft | 45.5 kg + 2.2 kg per inch over 5 ft |
| Devine | 1974 | 50 kg + 2.3 kg per inch | 45.5 kg + 2.3 kg per inch |
| Robinson | 1983 | 52 kg + 1.9 kg per inch | 49 kg + 1.7 kg per inch |
| Miller | 1983 | 56.2 kg + 1.41 kg per inch | 53.1 kg + 1.36 kg per inch |
These coefficients are as published by calculator.net’s ideal weight calculator; Wikipedia lists the Devine and Hamwi formulas. Hamwi’s formula is often remembered in pounds: 106 lb + 6 lb per inch for men and 100 lb + 5 lb per inch for women.
Same examples with every formula
Man, 5 ft 10 in (10 inches over 5 ft): Hamwi 48 + 27 = 75.0 kg; Devine 73.0 kg; Robinson 52 + 19 = 71.0 kg; Miller 56.2 + 14.1 = 70.3 kg.
Woman, 5 ft 5 in (5 inches over): Hamwi 45.5 + 11 = 56.5 kg; Devine 57.0 kg; Robinson 49 + 8.5 = 57.5 kg; Miller 53.1 + 6.8 = 59.9 kg.
Across the four formulas the answers span almost 5 kg for the man and 3.4 kg for the woman, a reminder that “ideal” weight is an estimate, not a precise target.
The formulas compared by height
Men (kg)
| Height | Hamwi | Devine | Robinson | Miller | Healthy BMI range |
|---|---|---|---|---|---|
| 5 ft 4 in | 58.8 | 59.2 | 59.6 | 61.8 | 48.9–65.8 |
| 5 ft 6 in | 64.2 | 63.8 | 63.4 | 64.7 | 52.0–70.0 |
| 5 ft 10 in | 75.0 | 73.0 | 71.0 | 70.3 | 58.5–78.7 |
| 6 ft 2 in | 85.8 | 82.2 | 78.6 | 75.9 | 65.4–88.0 |
Women (kg)
| Height | Hamwi | Devine | Robinson | Miller | Healthy BMI range |
|---|---|---|---|---|---|
| 5 ft 0 in | 45.5 | 45.5 | 49.0 | 53.1 | 43.0–57.8 |
| 5 ft 4 in | 54.3 | 54.7 | 55.8 | 58.5 | 48.9–65.8 |
| 5 ft 6 in | 58.7 | 59.3 | 59.2 | 61.3 | 52.0–70.0 |
| 5 ft 10 in | 67.5 | 68.5 | 66.0 | 66.7 | 58.5–78.7 |
The healthy BMI range is the weight that gives a BMI from 18.5 to 24.9 at that height, the same for men and women. To convert kilograms to pounds, multiply by 2.2046, or use the unit converter.
Why the formulas disagree
- Different purposes. Hamwi’s was a quick clinical rule of thumb and Devine’s was designed for drug dosing; Robinson and Miller later proposed modified versions of Devine’s formula, each with its own base weight and slope.
- Different slopes. Hamwi adds 2.7 kg per inch for men; Miller adds only 1.41. The gap widens with height: at 6 ft 2 in, Hamwi gives about 10 kg more than Miller.
- Straight lines for curved reality. Weight scales roughly with the square of height (that’s the idea behind BMI), but these formulas add a fixed amount per inch. They work best for average heights and drift at the extremes.
- Problems below 5 feet. The formulas were built for people of 5 feet and over. Applying them to shorter adults gives questionable results, sometimes implausibly low.
Ideal weight vs a healthy BMI range
Most health services today describe a healthy weight as a BMI between 18.5 and 24.9 for adults. Turning that into weight for your height gives a range rather than one number: at 5 ft 10 in (1.778 m), 18.5 × 1.778² ≈ 58.5 kg up to 24.9 × 1.778² ≈ 78.7 kg. A BMI of 22, near the middle, corresponds to about 69.5 kg at that height, close to the Robinson and Miller results.
A range is more realistic than a single “ideal”: two people of the same height can be equally healthy at weights 10 kg apart because of differences in muscle, bone and build. Our BMI formula guide explains the calculation, the BMI chart shows every height, and NICE in the UK recommends lower BMI thresholds for people of some ethnic backgrounds.
How to use these numbers sensibly
If you want a personal reference point, a practical approach is to look at where the formulas cluster and where that sits within your healthy BMI range. For a 5 ft 6 in woman, all four formulas land between 58.7 and 61.3 kg, comfortably inside the healthy range of 52 to 70 kg. That cluster is a reasonable “middle” to keep in mind, not a target you must hit.
More useful than any single number are trends and how you feel: whether your waist is less than half your height, whether your weight has been stable, and whether you can be active comfortably. If you’re well inside the healthy range and feel well, there’s usually no reason to chase a formula’s figure. If you’re outside it, small, sustained changes to daily calories and activity are what move the needle.
How doctors and pharmacists use IBW
In hospitals, IBW (usually Devine) is used for things where lean tissue matters more than total weight:
- Drug dosing. Some medicines are dosed on IBW or on an “adjusted body weight” between IBW and actual weight.
- Kidney function estimates, such as the Cockcroft-Gault equation for creatinine clearance.
- Ventilator settings: tidal volumes are set per kilogram of predicted body weight, a similar height-based formula.
These are professional calculations with their own rules; never adjust a medicine dose yourself based on an online formula.
Using centimetres
To use the formulas with centimetres, convert your height to inches (cm ÷ 2.54) and subtract 60, or use the per-centimetre version of Devine: 50 or 45.5 kg + 0.9 kg × (height in cm − 152). For 178 cm: 178 ÷ 2.54 = 70.1 inches, so Devine for a man is 50 + 2.3 × 10.1 ≈ 73.2 kg, and the per-cm version gives 50 + 0.9 × 26 = 73.4 kg.
Limits to keep in mind
- Muscle and frame. Athletes and people with a large frame can be healthy well above any formula’s number.
- Age. The formulas ignore age; healthy body composition changes over a lifetime.
- Ethnicity. Health risks at a given weight differ between populations, which the formulas don’t reflect.
- Children and teenagers. These are adult formulas; children need growth charts.
- Health is more than weight. Waist size, fitness, blood pressure and diet quality all matter.
If you’re thinking about changing your weight, start from your daily energy needs: see how to calculate TDEE and use the calorie calculator, and talk to a professional if you have a health condition.
FAQ
What is the formula for ideal body weight?
The Devine formula: 50 kg + 2.3 kg per inch over 5 feet for men, 45.5 kg + 2.3 kg per inch over 5 feet for women.
Which ideal body weight formula is most accurate?
None is “accurate” for an individual; they’re estimates. Devine is the clinical standard; Robinson and Miller give lower values for tall people.
What is my ideal weight at 5 ft 10?
Between about 70 and 75 kg by the four formulas for a man, and 66 to 68.5 kg for a woman. A healthy BMI range at that height is about 58.5 to 78.7 kg.
Is ideal body weight the same as a healthy weight?
Not quite. Health services define healthy weight as a BMI range, which allows for natural variation. IBW gives one number designed for clinical use.
Do the formulas work for people under 5 feet?
Poorly. They were built for adults of 5 feet and taller; use a BMI range instead.
Why do doctors use ideal body weight?
For drug dosing, kidney function estimates and ventilator settings, where lean tissue matters more than total weight.
Sources
- Wikipedia: Ideal body weight, Devine and Hamwi formulas and clinical uses (checked 7 November 2026).
- Calculator.net: Ideal weight calculator, Hamwi, Devine, Robinson and Miller coefficients (checked 7 November 2026).
- World Health Organization: Obesity and overweight fact sheet, adult BMI categories (checked 7 November 2026).
- Wikipedia: Body mass index (checked 7 November 2026).
Next steps
- See your healthy range with the BMI calculator.
- Plan daily calories with the calorie calculator.
- Or ask the AI workspace: “what’s a healthy weight at 5 ft 10?”