Frame Size Index Calculator

About this calculator

The frame size index is derived from the ratio of your height to your wrist circumference and is used to estimate whether you have a small, medium, or large bone structure — a variable that matters because standard height-weight tables and even BMI don't account for the fact that two people of identical height can have very different skeletal mass. This general concept traces back to the wrist-circumference method popularized in Frisancho's anthropometric reference standards and various insurance-industry height-weight tables from the mid-20th century, which used height-to-wrist ratio cutoffs that differ by sex.

Dietitians, fitness assessors, and bodybuilders sometimes use frame size alongside BMI or ideal-body-weight formulas, since a large-framed individual can carry more lean mass at a ‘normal’ weight than the same-height small-framed individual, meaning a frame-size adjustment helps avoid misclassifying naturally big-boned people as overweight, or small-framed people as underweight, based on generic height-weight charts alone.

This calculator takes your height, wrist circumference, and sex, computes the height-to-wrist ratio, and returns your frame size index along with a small/medium/large category.