How to use the Body Frame Size
- Measure your wrist circumference just below the wrist bone.
- Enter your height.
- Read the height-to-wrist ratio and your frame classification.
- Adjust ideal weight targets by roughly 10% up or down accordingly.
How the calculation works
The wrist method divides height by wrist circumference. For men, a ratio above 10.4 indicates a small frame, 9.6–10.4 medium and below 9.6 large; for women the thresholds are above 11.0, 10.1–11.0 and below 10.1. The wrist is used because it carries almost no muscle or fat, so its circumference reflects skeletal size alone — the elbow breadth method used in the original Metropolitan Life tables measures the same thing differently.
Frame size shifts ideal weight by around 10% in each direction from the medium-frame figure. It also partly explains why BMI misclassifies people: a large-framed individual carries more bone and lean mass at the same height, pushing BMI upward without any excess fat. Frame size is fixed in adulthood and cannot be trained, so it is a lens for interpreting other measurements rather than a target.
Ratio = height / wrist circumference ; thresholds differ by sexSource: Height-to-wrist-circumference frame size method derived from Metropolitan Life frame classification.
Worked example
A woman 165 cm tall with a 15.8 cm wrist.
- Ratio = 165 / 15.8 = 10.44.
- Female thresholds: >11.0 small, 10.1–11.0 medium.
- 10.44 falls in the medium band.
- Medium-frame ideal weight applies unadjusted.
Medium frame — standard ideal weight ranges apply without adjustment.
Frequently asked questions
Can I change my frame size?+
No. Skeletal dimensions are fixed in adulthood; only muscle and fat change.
Why does frame size matter?+
Ideal weight tables assume a medium frame, so large-framed people appear overweight against them.
Is the wrist method reliable?+
It is a reasonable proxy. Elbow breadth is the classical alternative and gives similar classifications.
Does frame size affect BMI?+
Yes, indirectly. A larger skeleton raises BMI at the same body fat percentage.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.