Ideal Body Weight Calculator | 4 Formulas: Hamwi, Devine, Robinson, Miller
Ideal Body Weight (IBW) is a clinical reference value used primarily for medication dosage calculations. This calculator computes IBW using four classic formulas: Hamwi (1964), Devine (1974), Robinson (1983), and Miller (1983). Each formula uses a base weight for 5 feet height plus an increment for each additional inch.
For men, the formulas range from 48-56 kg base weight with 1.4-2.7 kg per inch increments. For women, the base weights range from 45.5-53 kg with 1.36-2.2 kg per inch increments. We also show the average of all four formulas and compare against BMI-based healthy weight ranges.
IBW Calculation Input
Calculation Examples
Devine (1974): 50 + 2.3×9 = 50 + 20.7 = 70.7 kg
Robinson (1983): 52 + 1.9×9 = 52 + 17.1 = 69.1 kg
Miller (1983): 56.2 + 1.41×9 = 56.2 + 12.69 = 68.9 kg
Average: 70.3 kg | BMI 18.5-24.9: 56.7�?5.5 kg
Devine (1974): 45.5 + 2.3×4 = 45.5 + 9.2 = 54.7 kg
Robinson (1983): 49 + 1.7×4 = 49 + 6.8 = 55.8 kg
Miller (1983): 53.1 + 1.36×4 = 53.1 + 5.44 = 58.5 kg
Average: 55.8 kg | BMI 18.5-24.9: 48.0�?3.8 kg
Data Source and References
- [1] Hamwi GJ (1964). Clinical Nutrition: A Comprehensive Approach. Harper & Row.
- [2] Devine BJ (1974). Gentamicin therapy. Antimicrobial Agents and Chemotherapy, 6(2):377-379.
- [3] Robinson RD, Nelson DB (1983). Estimation of lean body mass and total body water. Clinical Chemistry, 29(9):1540-1546.
- [4] Miller RD (1983). Anesthesia. Churchill Livingstone.
Ideal Body Weight Formulas and Clinical Origins
The concept of ideal body weight originated in clinical pharmacology as a method to adjust medication dosages for patients of different sizes. Four formulas have become standard references in medical practice, each derived from different research contexts and population samples.
Hamwi Formula (1964)
The Hamwi formula was published in Gerald Hamwi's textbook Clinical Nutrition in 1964. It was designed for use in obesity research and drug dosage calculations. Male: IBW = 48 kg + 2.7 kg × (height_inches - 60). Female: IBW = 45.5 kg + 2.2 kg × (height_inches - 60). This formula uses larger per-inch increments than the others, producing higher IBW estimates especially for taller individuals.
Devine Formula (1974)
Devine's formula was developed specifically for estimating creatinine clearance and published in Antimicrobial Agents and Chemotherapy. Male: IBW = 50 kg + 2.3 kg × (height_inches - 60). Female: IBW = 45.5 kg + 2.3 kg × (height_inches - 60). Notably, Devine's formula uses the same 2.3 kg per inch increment for both men and women, simplifying the calculation.
Robinson Formula (1983)
Robinson and Nelson published their formula in Clinical Chemistry as part of a study on total body water estimation. Male: IBW = 52 kg + 1.9 kg × (height_inches - 60). Female: IBW = 49 kg + 1.7 kg × (height_inches - 60). This formula produces the lowest IBW estimates among the four standard formulas.
Miller Formula (1983)
Miller's formula appeared in his textbook Anesthesia and was designed for anesthetic drug dosing. Male: IBW = 56.2 kg + 1.41 kg × (height_inches - 60). Female: IBW = 53.1 kg + 1.36 kg × (height_inches - 60). This formula has the smallest per-inch increments and highest base weights, making it relatively insensitive to height variation.
Formula Comparison Table
| Formula | Male Base Weight | Male Increment | Female Base Weight | Female Increment | Publication Year |
|---|---|---|---|---|---|
| Hamwi | 48.0 kg | 2.70 kg/in | 45.5 kg | 2.20 kg/in | 1964 |
| Devine | 50.0 kg | 2.30 kg/in | 45.5 kg | 2.30 kg/in | 1974 |
| Robinson | 52.0 kg | 1.90 kg/in | 49.0 kg | 1.70 kg/in | 1983 |
| Miller | 56.2 kg | 1.41 kg/in | 53.1 kg | 1.36 kg/in | 1983 |
Limitations of IBW Formulas
Several important limitations should be recognized. First, all four formulas were developed on primarily Caucasian populations and may not apply to other ethnic groups. Second, they do not account for body composition—muscular individuals may weigh more than their IBW but still be healthy. Third, the formulas assume linear weight increase with height, which does not reflect actual anthropometric relationships across the height spectrum. Fourth, IBW should not be used as a goal weight for weight loss without considering BMI, body fat percentage, and overall health status.
Frequently Asked Questions
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The four classic ideal body weight (IBW) formulas are: Hamwi (1964) - Male: 48 kg + 2.7 kg/inch over 5ft, Female: 45.5 kg + 2.2 kg/inch over 5ft; Devine (1974) - Male: 50 kg + 2.3 kg/inch over 5ft, Female: 45.5 kg + 2.3 kg/inch over 5ft; Robinson (1983) - Male: 52 kg + 1.9 kg/inch over 5ft, Female: 49 kg + 1.7 kg/inch over 5ft; Miller (1983) - Male: 56.2 kg + 1.41 kg/inch over 5ft, Female: 53.1 kg + 1.36 kg/inch over 5ft.
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Each formula was derived from different population samples and clinical contexts. The Hamwi formula originated from drug dosage calculations for obese patients. Devine's formula was developed for estimating creatinine clearance. Robinson and Miller formulas came from studies on total body water and lean body mass estimation. The differences in coefficients reflect the varying population characteristics and clinical purposes for which each formula was designed.
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Ideal body weight is primarily used for medication dosage calculations, particularly for drugs where dosing needs adjustment based on body size. It is also used as a reference point for weight management goals. However, IBW should not be confused with healthy weight ranges defined by BMI, nor should it be used as a sole determinant of nutritional status or health.
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The classic IBW formulas were primarily derived from Caucasian populations and may not be accurate for other ethnic groups, children, adolescents, or individuals with extreme body compositions (very muscular or very obese). Modern clinical practice increasingly uses adjusted body weight (ABW) or actual body weight (ABW) with BMI-based dosing for many medications.