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Ideal body proportions.

John McCallum's formula uses wrist circumference as a stable reference point (bone size doesn't change with training) to calculate proportional targets for the rest of the body.

McCallum Formula

Wrist circumference

§ 01

About the McCallum method

John McCallum published this set of ratios in IronMan Magazine in 1974 as part of his "Keys to Progress" series. The premise: bone structure is fixed, so wrist size (a proxy for skeletal frame) predicts the maximum proportional muscle mass you can carry naturally.

The formula starts with chest at 6.5× wrist circumference, then derives the other measurements as percentages of chest. These represent classical bodybuilding proportions — they're targets for the look McCallum was writing about, not universal optima.

Use them as one reference point, not a prescription. Many athletes carry more or less than these proportions and remain healthy, strong, and proportional by their own aesthetic.