Dr. GJ Hamwi formula was established in 1964 and is based on the belief that a woman who is 5 feet tall should weigh 100 pounds. On the other hand, 5 feet tall man should weigh 106 pounds. For every additional inch over 5 feet, you add 5 pounds. If you are shorter, you should subtract 5 pounds for every 5-inch below 5 feet.
The formula is similar in many ways to Devine formula, but Hamwi went ahead to introduce a new concept of Body Frame in adjusting the ideal body weight. The results can be adjusted with either 10% for those with a big body frame or 10% for those with a smaller frame. Because of this adjustment, the Hamwi formulae is one of the most applied formulae in weight calculators.
The most important equipment is the stadiometer to get the right body height. You will also need a measuring tape to get the size of the wrist.
Procedure for calculating the ideal body weight
Using the stadiometer, get the right body height and apply the Hamwi formula shown below.
Men: Ideal Body Weight (in kilograms) = 48 kg + 2.7 kg for each inch over 5 feet
Women: Ideal Body Weight (in kilograms) = 45.5 kg + 2.2 kg for each inch over 5 feet.
If the wrist is 7 inches, the IBW remains the way it is. However, if the wrist size is more or less than 7 inches, you add or subtract 10% of ideal body weight respectively.
Note: 1 kilogram (kg) = 2.2 pounds (lb), 1 meter = 3.28084 feet
After establishing the ideal body weight, you will need to adjust it depending on whether the body is large, medium, or very large. Using the tape measure, get the correct reading of the wrist. If the wrist measures 7 inches, the body frame is medium, and you should not adjust the ideal body weight from the formulae. However, if the wrist is more than 7 inches, you need to add 10% of the ideal body weight. If the wrist is smaller, you are required to subtract 10% of the ideal body weight.
The target population
This formula can be used for average population and not those whose ranges fall within the extreme ends.
Advantages of Hamwi Formula
- The formula is very easy to apply especially when urgent applications such as medications in an emergency are required.
- Unlike other formulae that only use height, Hamwi appreciates that ideal body weight goes beyond that.
Disadvantages of Hamwi Formula
- Though it focuses on ideal body weight and adjustment for body frame, it still leaves out a lot of important factors.
- It is not suitable for those with extreme heights (very short or tall).
- The adjustment for the rib cage is very general
Though the Hamwi formula features great improvements compared to others especially the Broca Index and Devine Formula, it still has a lot of generalizations and leaves out so many factors that affect ideal weight.
1. Stehman CR, Buckley RG, Dos Santos FL, et al, Bedside estimation of patient height for calculating ideal body weight in the emergency department. J Emerg Med 2011;41:97-101
2. Bhumika Shah ., Kathryn Sucher, and Clarie B. Hollenbeck: Comparison of Ideal Body Weight Equations and Published Height-Weight Tables With Body Mass Index Tables for Healthy Adults in the United States.
3. Peterson, M., Diana M., George B., and Steven B. Universal equation for estimating ideal body weight and body weight at any BMI. Am J Clin Nutr May 1, 2016 103: 1197-1203