Weight Calculation Methods
Different Approaches to Calculating Ideal Weight
Various formulas have been developed over the years to estimate ideal body weight. Each method has its strengths and limitations, and they often produce slightly different results. Understanding these differences can help you interpret your ideal weight range more effectively.
The Hamwi Method (1964)
Developed by Dr. G.J. Hamwi for medication dosing purposes:
- Men: 48 kg (106 lb) for first 152 cm (5 ft) + 1.1 kg (2.2 lb) for each additional cm (2.5 in)
- Women: 45.5 kg (100 lb) for first 152 cm (5 ft) + 0.9 kg (2.0 lb) for each additional cm (2.5 in)
- ±10% adjustment for frame size
The Devine Formula (1974)
Created for medical use in drug dosage calculations:
- Men: 50 kg (110 lb) + 0.9 kg (2.0 lb) for each cm over 152 cm (5 ft)
- Women: 45.5 kg (100 lb) + 0.9 kg (2.0 lb) for each cm over 152 cm (5 ft)
The Robinson Formula (1983)
A modification of the Devine formula based on newer data:
- Men: 52 kg (114.6 lb) + 0.75 kg (1.65 lb) for each cm over 152 cm (5 ft)
- Women: 49 kg (108 lb) + 0.67 kg (1.48 lb) for each cm over 152 cm (5 ft)
The Miller Formula (1983)
Another modification of the Devine formula:
- Men: 56.2 kg (124 lb) + 0.9 kg (2.0 lb) for each cm over 152 cm (5 ft)
- Women: 53.1 kg (117 lb) + 0.9 kg (2.0 lb) for each cm over 152 cm (5 ft)
Comparison of Methods for a 175 cm (5'9") Male
| Method | Ideal Weight | Notes |
|---|---|---|
| Hamwi | 68.3-83.7 kg (150.6-184.6 lb) | Includes frame size adjustment |
| Devine | 70.7 kg (156 lb) | Single point estimate |
| Robinson | 69.3 kg (152.8 lb) | More conservative |
| Miller | 76.7 kg (169 lb) | Higher estimate |
Which Method is Most Accurate?
No single formula is perfect for everyone. The differences between methods highlight that ideal weight is a range, not a precise number. Our calculator combines multiple methods to give you a comprehensive range that accounts for these variations.
Key Insight: The variation between methods (up to 10% in some cases) demonstrates why it's valuable to consider multiple formulas when determining your healthy weight range.
Factors Not Accounted For
These formulas have limitations because they don't consider:
Muscle Mass
Athletes may weigh more due to muscle density.
Body Fat Distribution
Where fat is stored affects health risks.
Ethnic Differences
Body composition varies among ethnic groups.
Age-Related Changes
Muscle loss and fat redistribution occur with aging.
When to Use Which Method
Different methods may be more appropriate in specific situations:
| Method | Best For | Limitations |
|---|---|---|
| Hamwi | General population, accounts for frame size | Original data from 1964 may be outdated |
| Devine | Medical dosing calculations | May underestimate for taller individuals |
| Robinson | Modern general use | More conservative estimates |
| Miller | Taller individuals | Higher estimates may not suit all body types |