What frame size means
Two people of the same height can have very different bone structures. Frame size is a simple way to describe that difference, and it is used to refine ideal-weight estimates. The most common method compares your height with your wrist circumference, because the wrist carries little fat or muscle and reflects bone size well.
The height-to-wrist ratio
r = height ÷ wrist circumference, both in the same unit.
| Frame | Women | Men |
|---|---|---|
| Small | r above 11.0 | r above 10.4 |
| Medium | r from 10.1 to 11.0 | r from 9.6 to 10.4 |
| Large | r below 10.1 | r below 9.6 |
These cut-offs come from a method described by J. P. Grant in 1980 and still used in nutrition assessment.
Worked example
A woman who is 5 ft 5 in (65 in) tall has a 6-inch wrist.
- Ratio: 65 ÷ 6 = 10.83, a medium frame.
- Hamwi ideal weight for a woman: 100 lb for the first 5 feet + 5 lb per inch above, so 100 + 5 × 5 = 125 lb.
- With a medium frame, no adjustment: 125 lb. A small frame would give about 113 lb and a large frame about 138 lb.
For men, the Hamwi formula starts at 106 lb for 5 feet and adds 6 lb per inch.
How to measure your wrist
- Use a soft, non-stretch tape measure.
- Wrap it around the wrist just above the wrist bone, on the forearm side, where you would wear a watch.
- Keep it snug but do not compress the skin, and read to the nearest eighth of an inch or millimeter.
Some charts use elbow breadth instead, measured with calipers across the two bony points of the elbow with the arm bent at 90°. It is more precise but harder to do at home.
Limits
Frame size is a rough guide. It does not measure body fat or muscle, and the Hamwi formula was designed for quick dosing estimates, not as a health target. A healthy weight is better judged with several measures together, such as BMI, waist circumference, waist-to-height ratio and how you feel and function.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.