Jackson & Pollock 3-Site Skinfold Calculator: Body Fat Percentage

By PounceFit Team · Updated on 2026-10-06

Technical content for health and fitness professionals. It reproduces formulas and protocols published in the scientific literature, with the sources at the end of the page. It is not a recommendation and does not replace the judgment of the professional who runs the assessment.

Free Jackson & Pollock 3-site skinfold calculator: body fat percentage with sex-specific sites and the same math as PounceFit, the body assessment app.

The Jackson & Pollock 3-site skinfold calculator estimates body fat percentage from only three skinfolds, which makes the assessment faster. Like the 7-site version, it calculates body density and converts it to body fat with the Siri equation (Jackson and Pollock, 1978; Jackson, Pollock and Ward, 1980; Siri, 1961). The math is the same as in PounceFit, body assessment software, and you can record the measurements on the printable body assessment form.

Who it is for

Adults from the general population, within the ranges of the original studies: men aged 18 to 61 and women aged 18 to 55 (Jackson and Pollock, 1978; Jackson, Pollock and Ward, 1980). The sites differ by sex:

• Men: chest, abdominal and thigh.
• Women: triceps, suprailiac and thigh.

Formula

S = sum of the three skinfolds, in mm.

• Men: density = 1.10938 − 0.0008267 × S + 0.0000016 × S² − 0.0002574 × age
• Women: density = 1.0994921 − 0.0009929 × S + 0.0000023 × S² − 0.0001392 × age
• Body fat (%) = (4.95 ÷ density − 4.50) × 100

Worked example

Woman, 25 years old, 60 kg (132 lb). Skinfolds (mm): triceps 18, suprailiac 14, thigh 25.

1. S = 57 mm; S² = 3,249.
2. Density = 1.0994921 − 0.0009929 × 57 + 0.0000023 × 3,249 − 0.0001392 × 25 = 1.0468895.
3. Body fat = (4.95 ÷ 1.0468895 − 4.50) × 100 = 22.8%.
4. Fat mass = 13.7 kg; fat-free mass = 46.3 kg.

Limitations

• With fewer sites, a single inaccurate reading has more weight in the result. The 7-site version spreads that risk better.
• The result is an estimate, with an error of about 3 to 4 percentage points against the reference method (Heyward and Wagner, 2004).
• Outside the age ranges and populations of the original studies, accuracy may be lower (Heyward and Wagner, 2004).
• Use the standardized measurement sites (ACSM, 2021) and do not switch protocols between assessments of the same client.