How to calculate body fat percentage with skinfold calipers

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.

To calculate body fat percentage with skinfold calipers, you measure the skinfolds of a protocol, add them up, apply the protocol's equation to get body density and convert density to body fat with the Siri equation: body fat (%) = (4.95 ÷ density − 4.50) × 100 (Siri, 1961). With the Jackson & Pollock 3-site protocol, for example, a 35-year-old man with a 54 mm sum comes out at 16.8% body fat (Jackson and Pollock, 1978). The result is an estimate, with an error of about 3 to 4 percentage points against the reference method (Heyward and Wagner, 2004).

Step 1: choose the protocol

Each protocol sets which skinfolds to measure and which equation to use, and was built in a specific sample. The protocols with a calculator on this site:

To decide between the Jackson & Pollock versions, see 3-site vs 7-site.

Step 2: measure the skinfolds

• Measure on the right side, with the client standing and relaxed (ACSM, 2021).
• Locate and mark each site from the standard description. The 7 sites are described in Jackson & Pollock 7-site skinfold.
• Take at least two measurements at each site, in rotation, and use the mean; if the two differ by too much, measure again (ACSM, 2021).
• Follow the ISAK technique for pinching and reading the caliper, which reduces the difference between measurements and between assessors (Stewart et al., 2011).

Step 3: add up the skinfolds and calculate density

Add up the means, in millimeters. The density equation depends on the protocol. For the Jackson & Pollock 3-site protocol, with S = sum of the three skinfolds and age in years (Jackson and Pollock, 1978; Jackson, Pollock and Ward, 1980):

• 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

Other protocols use the logarithm of the sum, such as Guedes (1985) and Durnin and Womersley (1974). Each one's formulas are in its calculator.

Step 4: convert density to body fat

The Siri equation (1961) turns density into body fat percentage:

Body fat (%) = (4.95 ÷ density − 4.50) × 100

It assumes fixed densities for fat mass (0.90 g/cm³) and fat-free mass (1.10 g/cm³) (Siri, 1961). For groups whose fat-free mass departs from this value, such as children and older adults, specific conversion formulas exist (Heyward and Wagner, 2004).

Step 5: calculate the masses

• Fat mass (kg) = weight × body fat (%) ÷ 100
• Fat-free mass (kg) = weight − fat mass

Worked example

Man, 35 years old, 85 kg (187 lb), Jackson & Pollock 3-site protocol. Mean skinfolds (mm): chest 12, abdomen 24 and thigh 18.

1. Sum: S = 12 + 24 + 18 = 54 mm; S² = 2,916.
2. Density = 1.10938 − 0.0008267 × 54 + 0.0000016 × 2,916 − 0.0002574 × 35 = 1.10938 − 0.0446418 + 0.0046656 − 0.009009 = 1.0603948.
3. Body fat = (4.95 ÷ 1.0603948 − 4.50) × 100 = 16.8%.
4. Fat mass = 85 × 16.8 ÷ 100 = 14.3 kg. Fat-free mass = 85 − 14.3 = 70.7 kg.

The Jackson & Pollock 3-site calculator and the app reach 16.8%, 14.3 kg and 70.7 kg with these numbers. A 7-site example is in Jackson & Pollock 7-site skinfold.

Limits of the calculation

• Equation error. Even with good technique, the error is about 3 to 4 percentage points against the reference method (Heyward and Wagner, 2004).
• Population. Outside the age range and profile of the original sample, accuracy may be lower (Heyward and Wagner, 2004).
• Technique. Site location, pinch technique and caliper all weigh on the result (Stewart et al., 2011).
• Comparison. Results from different protocols, or from skinfolds and bioimpedance, are not comparable with each other. See bioimpedance vs skinfolds.

To read the result against reference ranges by sex and age, see ideal body fat percentage.

The calculation in PounceFit

In PounceFit, the body assessment software, the professional picks the protocol when creating the assessment and enters two measurements per skinfold; the app works out the mean, the sum, density, body fat percentage and the masses, with the same math as the calculators on this site. The app takes 10 skinfold sites and offers five protocols for new assessments: Jackson & Pollock 7-site and 3-site, Guedes, Faulkner and Durnin & Womersley. To record measurements on paper, there is the printable body assessment form.