CALCULATOR
Devine, Hamwi and Robinson Formulas
The clinical ideal body weight equations run side by side, with the spread between them and an honest account of what they were actually built for.
These formulas date from clinical dosing work, not body composition. Treat the output as a wide range, not a verdict.
Devine, Hamwi, Robinson and Miller
These four equations all answer the same question, ideal body weight from height and sex, and all four give different answers. This page runs them together so you can see the spread rather than trusting whichever one a given calculator happened to use.
All were developed for clinical purposes rather than as personal weight targets. Devine, the most widely used, was published in 1974 in the context of medication dosing. Hamwi came from diabetes management in 1964, and Robinson and Miller both followed in 1983 as attempts to fit better data.
They remain in genuine clinical use for drug dosing and ventilator settings, where a standardised reference weight is more appropriate than actual bodyweight. As a personal goal they are a wide reference range at best, because they cannot see muscle, frame size or body composition.
The four clinical formulas
Men: 50.0 + 2.3 per inch over 5 ft
Women: 45.5 + 2.3 per inch over 5 ft
Hamwi (1964)
Men: 48.0 + 2.7 per inch Women: 45.5 + 2.2 per inch
Robinson (1983)
Men: 52.0 + 1.9 per inch Women: 49.0 + 1.7 per inch
Miller (1983)
Men: 56.2 + 1.41 per inch Women: 53.1 + 1.36 per inch
What each returns at common heights, men
| Height | Devine | Hamwi | Robinson | Miller | Spread |
|---|---|---|---|---|---|
| 165 cm | 61.2 kg | 62.1 kg | 61.4 kg | 63.2 kg | 2.0 kg |
| 175 cm | 70.3 kg | 72.8 kg | 69.0 kg | 68.8 kg | 4.0 kg |
| 185 cm | 79.4 kg | 83.4 kg | 76.5 kg | 74.3 kg | 9.1 kg |
Notice the spread widening with height. At 185 cm the four formulas disagree by over nine kilograms for the same person, which is a fair indication of how precisely any of them describes an individual.
Why these formulas exist
None of them was created to tell people what to weigh. Devine was published in the context of gentamicin dosing, and the others followed for similar clinical purposes. Many drugs, particularly those distributed in lean tissue, are dosed against ideal or adjusted body weight rather than actual weight, because dosing a heavier patient on total mass would overshoot.
That origin explains their limitations as a personal target. They take only height and sex as inputs. They cannot account for frame size, muscle mass or body composition, and they were derived from limited historical populations.
Where they are genuinely used
| Use | Why ideal weight rather than actual |
|---|---|
| Medication dosing | Some drugs distribute in lean tissue, not fat |
| Ventilator tidal volume | Lung size tracks height, not bodyweight |
| Renal function estimation | Standardising across body sizes |
| Nutrition support calculations | Estimating requirements in clinical settings |
What to use instead as a personal target
- Healthy BMI range is wider and more honest than a single figure, though it shares the muscle blind spot.
- Waist to height ratio under 0.5 captures fat distribution, which these formulas ignore entirely.
- Body fat percentage separates lean mass from fat, which is what actually differs between two people of the same height.
- Performance and how you feel at a given weight, which no equation can supply.
A trained person will commonly sit above every figure these formulas produce while being in excellent health. That is not the formula failing; it is being used for something it was never designed to do.
Frequently asked questions
What is the Robinson formula?
Which ideal body weight formula is most accurate?
Why do the formulas disagree so much?
Should I use ideal body weight as a goal?
Sources
- Devine BJ. Gentamicin therapy. Drug Intelligence and Clinical Pharmacy, 1974.
- Hamwi GJ. Therapy: changing dietary concepts. American Diabetes Association, 1964.
- Robinson JD et al. Determination of ideal body weight for drug dosage calculations. American Journal of Hospital Pharmacy, 1983.
- Miller DR et al. Determination of ideal body weight for drug dosage calculations. American Journal of Hospital Pharmacy, 1983.
- Pai MP, Paloucek FP. The origin of the ideal body weight equations. Annals of Pharmacotherapy, 2000.
- National Institutes of Health, Office of Dietary Supplements. Nutrient fact sheets. ods.od.nih.gov
- NHS. Nutrition and health guidance. nhs.uk
- US Departments of Agriculture and Health and Human Services. Dietary Guidelines for Americans, 2025-2030. dietaryguidelines.gov
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General information, not medical advice. Consult a qualified professional before changing your diet, especially with a medical condition.