Last updated: May 2026
The Hamwi method is an ideal body weight formula developed by Dr. G.J. Hamwi in 1964. It uses a simple rule — a base weight at 5 feet plus an increment per additional inch — making it one of the easiest IBW calculations to do without a calculator. Here’s the full formula, tables, and worked examples.
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The Hamwi Formula
For men:
106 lbs for the first 5 feet of height + 6 lbs for each additional inch
Adjust ±10% for small or large frame
For women:
100 lbs for the first 5 feet of height + 5 lbs for each additional inch
Adjust ±10% for small or large frame
Sometimes called the “106 + 6 rule” (men) or “100 + 5 rule” (women). Both are easy to remember and calculate mentally.
In metric (kg):
- Men: 48.0 kg + 2.7 kg per inch over 5 feet
- Women: 45.5 kg + 2.2 kg per inch over 5 feet
Worked Examples
Example 1: Man who is 5’10”
Inches over 5 feet = 10
Hamwi IBW = 106 + (6 × 10) = 166 lbs (medium frame)
- Small frame (−10%): 166 − 16.6 = ~149 lbs
- Large frame (+10%): 166 + 16.6 = ~183 lbs
Example 2: Woman who is 5’6″
Inches over 5 feet = 6
Hamwi IBW = 100 + (5 × 6) = 130 lbs (medium frame)
- Small frame (−10%): 130 − 13 = ~117 lbs
- Large frame (+10%): 130 + 13 = ~143 lbs
Example 3: Man who is 6’2″
Inches over 5 feet = 14
Hamwi IBW = 106 + (6 × 14) = 190 lbs (medium frame)
- Small frame: ~171 lbs
- Large frame: ~209 lbs
Related Reading
Hamwi IBW Table — Men (Medium Frame)
| Height | Small Frame (−10%) | Medium Frame | Large Frame (+10%) |
|---|---|---|---|
| 5′ 0″ | 96 lb | 106 lb | 117 lb |
| 5′ 1″ | 101 lb | 112 lb | 123 lb |
| 5′ 2″ | 106 lb | 118 lb | 130 lb |
| 5′ 3″ | 112 lb | 124 lb | 136 lb |
| 5′ 4″ | 117 lb | 130 lb | 143 lb |
| 5′ 5″ | 122 lb | 136 lb | 150 lb |
| 5′ 6″ | 128 lb | 142 lb | 156 lb |
| 5′ 7″ | 133 lb | 148 lb | 163 lb |
| 5′ 8″ | 139 lb | 154 lb | 169 lb |
| 5′ 9″ | 144 lb | 160 lb | 176 lb |
| 5′ 10″ | 149 lb | 166 lb | 183 lb |
| 5′ 11″ | 155 lb | 172 lb | 189 lb |
| 6′ 0″ | 160 lb | 178 lb | 196 lb |
| 6′ 1″ | 166 lb | 184 lb | 202 lb |
| 6′ 2″ | 171 lb | 190 lb | 209 lb |
| 6′ 3″ | 176 lb | 196 lb | 216 lb |
| 6′ 4″ | 182 lb | 202 lb | 222 lb |
Hamwi IBW Table — Women (Medium Frame)
| Height | Small Frame (−10%) | Medium Frame | Large Frame (+10%) |
|---|---|---|---|
| 4′ 10″ | 81 lb | 90 lb | 99 lb |
| 4′ 11″ | 86 lb | 95 lb | 105 lb |
| 5′ 0″ | 90 lb | 100 lb | 110 lb |
| 5′ 1″ | 95 lb | 105 lb | 116 lb |
| 5′ 2″ | 99 lb | 110 lb | 121 lb |
| 5′ 3″ | 104 lb | 115 lb | 127 lb |
| 5′ 4″ | 108 lb | 120 lb | 132 lb |
| 5′ 5″ | 113 lb | 125 lb | 138 lb |
| 5′ 6″ | 117 lb | 130 lb | 143 lb |
| 5′ 7″ | 122 lb | 135 lb | 149 lb |
| 5′ 8″ | 126 lb | 140 lb | 154 lb |
| 5′ 9″ | 131 lb | 145 lb | 160 lb |
| 5′ 10″ | 135 lb | 150 lb | 165 lb |
| 5′ 11″ | 140 lb | 155 lb | 171 lb |
| 6′ 0″ | 144 lb | 160 lb | 176 lb |
Where the Hamwi Method Is Still Used
Despite its age, the Hamwi formula remains in active clinical use:
- Drug dosing: Medications like insulin, aminoglycoside antibiotics, and some chemotherapy agents are dosed by IBW rather than actual body weight
- Nutrition support: Caloric and protein requirements in hospital parenteral nutrition are calculated using IBW (or adjusted body weight for obese patients)
- Fluid management: Maintenance fluid calculations reference IBW, particularly in pediatric and critical care settings
- Fitness benchmarking: Used as a rough personal target, particularly when combined with the ±10% frame adjustment
Related Reading
Limitations of the Hamwi Method
- Only considers height and sex — no adjustment for muscle mass, body fat, bone density, or age
- Produces results toward the lower end of the healthy BMI range — many healthy, active people exceed their Hamwi IBW due to muscle mass
- Was designed for drug dosing, not weight loss targets or appearance goals
- Does not differentiate between races or ethnicities, despite known differences in body composition at the same weight
- The ±10% frame adjustment is crude — a small-framed person and a large-framed person at the same height can healthily differ by more than 20% in weight
For personal health use, treat the Hamwi IBW as a rough reference point rather than a precise target. The healthy BMI range (18.5–24.9) and body fat percentage are more appropriate health-based benchmarks for most people.
Frequently Asked Questions
Is the Hamwi method accurate?
The Hamwi method gives a reasonable estimate for most average adults but has meaningful limitations. It works well for clinical drug dosing purposes (its original intent) but can underestimate a healthy weight for muscular individuals and doesn’t account for body composition. For health assessment, it’s best used alongside body fat percentage and waist circumference measurements.
What is the Hamwi IBW for a 5’9″ male?
Hamwi IBW for a 5’9″ man (medium frame): 106 + (6 × 9) = 160 lbs. Small frame: ~144 lbs. Large frame: ~176 lbs. The healthy BMI range for a 5’9″ man is 128–162 lbs — the Hamwi medium frame sits at the top of this range.
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Our ideal weight calculator applies the Hamwi formula for your height and sex, with small, medium, and large frame results.
