How is this different from the US Navy circumference method?

The Navy method uses only a tape measure (neck, waist, hip); this method needs a skinfold caliper and measures subcutaneous fat thickness directly at specific sites, then runs the sum through a different regression equation. Both convert to a fat percentage using the same Siri equation, but they can give slightly different results for the same person.

How accurate is the Jackson-Pollock method?

In the hands of an experienced, consistent tester, it's generally considered accurate to within about 3–4% of DEXA-measured body fat — but caliper technique (site location, pinch pressure, reading timing) is a major source of error for inexperienced users. Have the same person measure you each time for the most useful trend data.

Why does age affect the result?

The regression equations include an age term because body density at a given skinfold thickness tends to decrease slightly with age, reflecting typical age-related changes in fat distribution and tissue composition found in the original research population.

Skinfold Body Fat Calculator

Estimate body fat percentage from 3-site caliper skinfold measurements using the Jackson-Pollock regression formula and the Siri body-density equation.

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Formula: Body density (men) = 1.10938 − 0.0008267×sum + 0.0000016×sum² − 0.0002574×age; Siri: %BF = 495/density − 450

Worked examples

Man, 30, chest 12 mm, abdomen 18 mm, thigh 15 mm
A lean, trained male with low skinfold thicknesses across all three sites.
Woman, 28, triceps 14 mm, suprailiac 16 mm, thigh 20 mm
A fit, recreationally active woman using the triceps/suprailiac/thigh site combination.
Man, 45, chest 20 mm, abdomen 28 mm, thigh 18 mm
A middle-aged man with a moderate skinfold sum, showing how age lowers the estimated density (and raises fat%) versus a younger person with the same measurements.

What this calculator estimates

This tool estimates body fat percentage from skinfold caliper measurements at three anatomical sites, using the Jackson-Pollock 3-site method — one of the most widely used caliper-based body-composition protocols in exercise science and personal training. It's a different measurement approach from this hub's tape-measure-only US Navy body-fat calculator: instead of circumferences, it measures the thickness of a pinched fold of skin and underlying fat at specific points on your body.

The formula and its source

The method comes from Jackson & Pollock's 1978 research (extended for women by Jackson, Pollock & Ward, 1980), which developed separate regression equations for men and women predicting body density from the sum of three skinfold measurements and age. For men, the sites are chest, abdomen and thigh; for women, they're triceps, suprailiac (just above the hip bone) and thigh — the original research found these site combinations gave the best prediction accuracy for each sex, which is why the protocol differs rather than using one universal set of sites. The resulting body density is converted to a fat percentage using the Siri (1961) equation, the same conversion this hub's Navy-method body-fat calculator uses.

How to measure

Pinch a fold of skin and fat firmly between your thumb and forefinger, away from the underlying muscle, then apply the caliper about a centimeter below the pinch, letting the reading settle for 1–2 seconds. Take each site twice and average the readings — skinfold measurement has real technique-dependent variability, so consistency across attempts matters more than getting a single "perfect" reading. Measure on the same side of the body each time (traditionally the right side).

Why age is part of the formula

Body density at a given skinfold thickness tends to shift somewhat with age, reflecting typical age-related changes in tissue composition found in the original research population — the equations include an age term to account for this rather than assuming a fixed relationship between skinfold thickness and body fat regardless of age.

Accuracy and limits

In the hands of an experienced, consistent tester, Jackson-Pollock is generally considered accurate to within about 3–4 percentage points of DEXA-measured body fat — comparable to the Navy method. The biggest source of error is technique: caliper pinch pressure, exact site location and reading timing all vary between testers and even between attempts by the same tester, especially for beginners. If you're tracking your own progress over time, having the same person (ideally a trained one) measure you the same way each time matters more than which specific formula is used.

Not medical advice

This tool provides a general body-composition estimate from a published research formula. It is not a diagnostic or medical measurement, and it doesn't account for individual variation beyond what the regression captures — use it to track your own trend over weeks or months, and speak with a qualified professional for anything beyond general fitness tracking.

Frequently asked questions

Which 3 sites do I measure?: For men: chest, abdomen and thigh. For women: triceps, suprailiac (just above the hip bone) and thigh. Jackson and Pollock's original research found these site combinations gave the best prediction accuracy separately for each sex, which is why the protocol differs by sex rather than using one universal set of sites.
How is this different from the US Navy circumference method?: The Navy method uses only a tape measure (neck, waist, hip); this method needs a skinfold caliper and measures subcutaneous fat thickness directly at specific sites, then runs the sum through a different regression equation. Both convert to a fat percentage using the same Siri equation, but they can give slightly different results for the same person.
How accurate is the Jackson-Pollock method?: In the hands of an experienced, consistent tester, it's generally considered accurate to within about 3–4% of DEXA-measured body fat — but caliper technique (site location, pinch pressure, reading timing) is a major source of error for inexperienced users. Have the same person measure you each time for the most useful trend data.
Why does age affect the result?: The regression equations include an age term because body density at a given skinfold thickness tends to decrease slightly with age, reflecting typical age-related changes in fat distribution and tissue composition found in the original research population.

These calculators give general estimates from published formulas. They are not medical advice and do not account for your individual health; talk to a qualified professional before changing your diet or training.