Body Frame Size Calculator
Small, medium, or large? Your bone structure changes what a healthy weight looks like for you. This calculator uses the NIH / MedlinePlus wrist-circumference method — a fast, accepted proxy for skeletal size.
Fine bones — aim toward the lower end of the healthy weight range.
How to measure your wrist (30 seconds)
- Wrap a soft tape measure around your dominant wrist, just above the bone that sticks out.
- Snug but not tight. Read the number.
- No tape? Wrap your thumb and middle finger around the same spot: overlap = small, just touching = medium, gap = large.
Why frame size matters
Two people with the same height can healthily weigh 10–15 lbs apart if one has small bones and the other has large bones. Ignoring frame size is why generic BMI ranges feel wrong to slim-boned or broad-boned people. The calculation is used by the NIH, MedlinePlus, and clinical dietitians.
Ready for a full healthy weight range? Use the Quick Target Weight calculator — it already factors in frame size.
Frequently asked questions
What is body frame size?
Body frame size is a measure of skeletal bone structure. It helps explain why two people of the same height can have very different healthy weights.
How do I measure my wrist for frame size?
Wrap a soft tape measure around your dominant wrist just above the bony bump. Use a snug but not tight fit. Compare the measurement to your height using the NIH / MedlinePlus method.
Can frame size change my ideal weight?
Yes. A large frame typically adds 10-15 pounds to the healthy end of the range, while a small frame shifts it lower. The Quick Target Weight calculator already applies this adjustment.
What if I don't have a tape measure?
Use the thumb-and-finger test: wrap your thumb and middle finger around your wrist. Overlap = small frame, touching = medium frame, gap = large frame.