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About this tool
Find whether you have a small, medium or large body frame from your wrist circumference and height, with a frame-adjusted ideal weight.
Body frame size classifies your skeleton as small, medium or large by reading your wrist circumference against your height — the same wrist-and-height table published by MedlinePlus, plus the height-divided-by-wrist ratio used in clinical nutrition. Enter a wrist measurement taken just above the wrist bone and your height, and both methods are shown side by side along with a Hamwi ideal-weight figure adjusted 10% down for a small frame or 10% up for a large one. It is a quick way to understand why two people of the same height can carry visibly different amounts of bone and still be built normally.
Open Body Frame Size Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
The MedlinePlus wrist bands and the height-to-wrist ratio table are shown together, so you can see when you sit on a boundary.
Applies the conventional Hamwi 10% small/large adjustment instead of quoting a single average figure.
Enter height in centimetres or feet and inches and the wrist in centimetres or inches; conversions are handled for you.
Wrap a flexible tape around the smallest part of your wrist, just past the wrist bone toward the hand, on your dominant arm. Keep it snug but not compressing the skin, and read the number to the nearest tenth of a centimetre or the nearest eighth of an inch — a difference of a quarter inch can move you a whole frame category.
For men over 5 ft 5 in, a wrist above 7.5 inches is a large frame, 6.5 to 7.5 inches is medium and under 6.5 inches is small. For women the cut-offs depend on height: over 5 ft 5 in a wrist above 6.5 inches is large, between 5 ft 2 in and 5 ft 5 in the large threshold is 6.25 inches, and under 5 ft 2 in it is 5.75 inches.
It shifts the reference figure by roughly 10% in each direction. Using the Hamwi formula, a 178 cm man has a medium-frame reference weight near 75 kg, about 68 kg with a small frame and about 83 kg with a large one. These are population reference points, not personal targets — body composition, muscle mass and health markers matter more.
The wrist-and-height table uses fixed height brackets, so a person a fraction under a bracket edge is judged against a different cut-off than someone a fraction above it, while the ratio method varies continuously. When the two disagree you are sitting near a boundary and are best described as being between frames. Frame size is descriptive only; ask a clinician or dietitian before using it to set a weight goal.
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