Body Frame Size Calculator
Your body frame size from wrist circumference and height — the measure that adjusts an ideal weight range for skeletal build.
Frame size is estimated from the ratio of height to wrist circumference, which is a reasonable proxy for skeletal size because the wrist carries almost no fat or muscle.
How the body frame size calculator works
Frame size is estimated from the ratio of height to wrist circumference, which is a reasonable proxy for skeletal size because the wrist carries almost no fat or muscle.
It matters because ideal-weight formulas assume a medium frame. A large-framed person can carry 10% more weight at the same health, and a small-framed person 10% less. Without the adjustment the target is simply wrong for a third of people.
Formula: ratio = height / wrist circumference
Worked examples
| Inputs | Frame size | Note |
|---|---|---|
| 175 cm, 17 cm wrist, male | medium frame | medium frame |
| A slighter build | small frame | small frame |
| A heavier build | large frame | large frame |
FAQFrequently asked questions
How do I measure my frame size?
Wrap a tape around the smallest part of your wrist, just below the bone, and divide your height by that circumference.
Why the wrist?
Because it carries almost no fat or muscle, so its circumference is close to a direct measure of skeletal size.
Does frame size really change ideal weight?
By about 10% either way. Ideal-weight formulas assume a medium frame, which is wrong for roughly a third of people.
Is a large frame the same as being overweight?
No. Frame is skeletal; it is fixed and unrelated to body fat. A large-framed person simply has a higher healthy weight.
Is this precise?
It is a rule of thumb, and elbow breadth is a somewhat better measure. Neither is a substitute for a body-composition assessment.
Where these figures come from
- Mifflin MD et al., "A new predictive equation for resting energy expenditure in healthy individuals", Am J Clin Nutr 1990 — the BMR equation used here
- World Health Organization — Waist circumference and waist–hip ratio (2008 expert consultation) — waist-to-hip cut-offs
- Tanaka H, Monahan KD, Seals DR, "Age-predicted maximal heart rate revisited", J Am Coll Cardiol 2001 — 208 − 0.7 × age
- Nathan DM et al., "Translating the A1C assay into estimated average glucose values" (ADAG), Diabetes Care 2008 — eAG = 28.7 × A1c − 46.7
- Mosteller RD, "Simplified calculation of body-surface area", N Engl J Med 1987 — BSA = √(height × weight / 3600)
- NHS — national health guidance
Last checked: September 2026. The equations are fixed by their published papers and do not change with tax years or regulations; the thresholds quoted in verdicts name the body that set them.