A worked example
A male at 5'9" with a 7-inch wrist has a height-to-wrist ratio of about 9.86 — landing in the "Medium" frame category.
Frequently asked questions
Why use wrist circumference for this?
Wrist size is relatively unaffected by body fat or muscle gain — it's mostly determined by bone structure, which makes it a reasonably stable proxy for underlying frame size compared to measurements that change with diet or training.
Are ectomorph/mesomorph/endomorph real scientific categories?
They originate from a mid-20th century somatotype classification system that's since been largely superseded in formal kinanthropometry — but the terms remain widely used informally in fitness culture as a loose, approximate way to describe build tendencies.
This calculator provides a simplified estimate for general informational purposes only, not a rigorous somatotype analysis or medical assessment.