Body Frame Size Calculator

Body frame size is assessed with the wrist circumference method, a quick anthropometric measurement that sorts a skeleton into small, medium or large framed. The wrist is used because it is almost pure bone and skin: there is very little muscle or fat there to confuse the reading, which is exactly what makes it a decent proxy for skeletal size when a caliper is not to hand.

The formula uses the r-value, height divided by wrist circumference:

r = Height (cm) / Wrist Circumference (cm)

Because it is a ratio of two lengths, the units cancel. Measure both in inches and you get the same number.

Frame size for women:

• Small frame: r above 11.0
• Medium frame: r from 10.1 to 11.0
• Large frame: r below 10.1

Frame size for men:

• Small frame: r above 10.4
• Medium frame: r from 9.6 to 10.4
• Large frame: r below 9.6

The direction trips people up, so it is worth stating plainly: a higher r means a smaller frame. A high ratio is a thin wrist relative to a tall body.

An alternative method uses elbow breadth measured with calipers against sex and height tables from the Metropolitan Life Insurance Company (1983 reference values). It is more accurate and needs equipment most people do not own.

Worked Example: A woman who is 165 cm tall with a wrist circumference of 15.5 cm:

• r = 165 / 15.5 = 10.65
• 10.1 is below 10.65, which is below 11.0, so: Medium frame

What frame size does to a target weight

The Hamwi formula gives a single ideal body weight, then adjusts it by frame. For women it is 100 lbs for the first 5 feet plus 5 lbs for every inch above that. Our example is 5 feet 5 inches, so 100 + 25 = 125 lbs, and that figure is the medium-frame answer.

The frame adjustment is ±10% of that base:

So the frame decision moves the target by 25 pounds, which is the whole reason anyone measures a wrist. Note that Hamwi produces a single number rather than a range; it dates from 1964 and was built for calculating insulin doses, not for telling people what to weigh. Treat it as one reference point beside a BMI range, not as a goal.

Frame size has no effect on BMI at all, since BMI knows only height and weight. That is a fair criticism of BMI: two people of identical height and weight, one broad-boned and one fine-boned, get the same number and do not have the same healthy weight.