What is estimated
Body density and estimated body-fat percentage from 3-site or 7-site caliper measurements.
Skinfold Body Fat Calculator
Estimated body fat from skinfolds
Enter your values, then calculate to see a verified result.
Reference range
How this result is calculated
A clear calculation path based on your inputs.
Inputs usedReview the information used for this result.
Full calculation and sourcesReview the equation, normalized inputs, assumptions, and version.
Versioned calculationFormula v1.0.0
Method
The calculator routes to sex-specific Jackson-Pollock equations and keeps Siri and Brozek conversions visible.
Important boundary
Caliper technique, site selection, age range, operator skill, and equation population can move the estimate by several percentage points.
Choose the exact method3-site and 7-site equations require different anatomical measurements.
Do not substitute one site for another.Estimate body densityApply the sex-specific sum, squared-sum, and age terms.
Keep millimeters and full precision.Convert density to body fatUse Siri or Brozek and keep both visible.
Formula choice can move the result.Interpretation
% is the selected skinfold-equation estimate.
Repeat the same sites and technique; operator consistency matters.
Siri and Brozek remain visible to expose density-conversion sensitivity.
Use this result
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Related calculators and resources
Method and test recordFormula v1.0.0
- Recorded scope
- health-body-composition
- Publisher
- CalculatorGeek
- Recorded review date
- 2026-10-04
- Next source review
- 2027-10-04
- Definition fixtures
- 4 configured scenarios
- Published examples
- 4 shown below
Recorded method
Independently sum the required sites, evaluate every sex/method branch, convert density with Siri and Brozek, and verify unit, age, and invalid-input boundaries.
These records describe the published model and reference tests. A test-case count is not a certification of every possible input or an independent specialist review. Editorial policy
Known limitations
- Operator and site-placement error can materially change the sum.
- The equations estimate body density for source populations and may not generalize to every person.
- Siri and Brozek conversions make different assumptions about fat-free tissue density.
- Skinfolds do not directly measure visceral fat and are not equivalent to DXA.
Method sources
- Jackson and Pollock (1982): Generalized body-composition equations for adults
- Pollock et al. (1976): Body-density prediction in men
- Jackson, Pollock and Ward (1980): Generalized equations for women
Latest model update
2026-10-04 - Initial CalculatorGeek shared-system implementation with source-backed method, fixtures, content, and result journey.
Reference inputs and expected results
Up to 12 examples from the configured definition fixtures are shown. Expected values use the stated output units; invalid inputs are intended to be rejected.
| Case | Inputs | Expected result |
|---|---|---|
| male 3-site reference | Skinfold method: three; Equation sex term: male; Density-to-fat conversion: siri; Age: 30 years; Body weight: 75 kg; Chest skinfold: 12 mm; Abdomen skinfold: 20 mm; Thigh skinfold: 18 mm; Triceps skinfold: 0 mm; Suprailiac skinfold: 0 mm; Midaxillary skinfold: 0 mm; Subscapular skinfold: 0 mm | Selected skinfold sum: 50 mm; Estimated body density: 1.064323 g/mL; Siri body-fat estimate: 15.084378 % (allowed numeric tolerance: 0.001) |
| female 3-site route | Skinfold method: three; Equation sex term: female; Density-to-fat conversion: siri; Age: 35 years; Body weight: 62 kg; Chest skinfold: 0 mm; Abdomen skinfold: 0 mm; Thigh skinfold: 22 mm; Triceps skinfold: 18 mm; Suprailiac skinfold: 20 mm; Midaxillary skinfold: 0 mm; Subscapular skinfold: 0 mm | Selected skinfold sum: 60 mm; Estimated body density: 1.0433261 g/mL; Siri body-fat estimate: 24.444184 % (allowed numeric tolerance: 0.001) |
| male 7-site route | Skinfold method: seven; Equation sex term: male; Density-to-fat conversion: brozek; Age: 30 years; Body weight: 80 kg; Chest skinfold: 12 mm; Abdomen skinfold: 20 mm; Thigh skinfold: 18 mm; Triceps skinfold: 14 mm; Suprailiac skinfold: 16 mm; Midaxillary skinfold: 13 mm; Subscapular skinfold: 15 mm | Selected skinfold sum: 108 mm; Estimated body density: 1.06278848 g/mL; Brozek body-fat estimate: 15.800897 % (allowed numeric tolerance: 0.002) |
| invalid age | Skinfold method: three; Equation sex term: male; Density-to-fat conversion: siri; Age: 12 years; Body weight: 75 kg; Chest skinfold: 12 mm; Abdomen skinfold: 20 mm; Thigh skinfold: 18 mm; Triceps skinfold: 0 mm; Suprailiac skinfold: 0 mm; Midaxillary skinfold: 0 mm; Subscapular skinfold: 0 mm | Reject invalid input: age |
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On this page
What the Skinfold Body Fat Calculator answers
Estimate adult body-fat percentage from Jackson-Pollock 3-site or 7-site skinfolds, then compare Siri and Brozek density conversions.
The calculator conditionally requests the correct anatomical sites and shows body density, skinfold sum, fat mass, and lean mass without hiding method sensitivity.
Start with the Health calculators hub when you need to choose a different body-measurement method.
How to use the Skinfold Body Fat Calculator
- Choose 3-site or 7-site and the published sex-specific equation set.
- Measure only the displayed anatomical sites with calipers in millimeters.
- Enter age and current body weight.
- Compare Siri and Brozek estimates and keep method and technique consistent for trends.
For a complementary body-measurement workflow, use the Body Fat Calculator. Compare a circumference-based estimate.
Formula, variables and method
The Jackson-Pollock equations first estimate body density from the selected skinfold sum, its square, and age. The 3-site measurements are chest, abdomen, and thigh for the male equation; triceps, suprailiac, and thigh for the female equation. The 7-site method adds chest, midaxillary, triceps, subscapular, abdomen, suprailiac, and thigh for both equation sets.
Siri: body fat % = 495 / density - 450. Brozek: body fat % = 457 / density - 414.2.
To compare this method with a different input model, open the Lean Body Mass Calculator. Compare height-weight regression estimates.
Worked examples and boundary checks
Male 3-site example
At age 30 with chest 12 mm, abdomen 20 mm, and thigh 18 mm, the sum is 50 mm. The equation gives density about 1.0652 g/mL and Siri body fat about 14.7%.
Method-boundary check
Switching to 7-site requires four additional sites; the calculator does not reuse a 3-site sum as if it were a 7-site result.
How to interpret the result
The result is an equation estimate whose repeatability depends heavily on measurement technique. The trend may be more useful than the absolute value when protocol is consistent.
- Operator and site-placement error can materially change the sum.
- The equations estimate body density for source populations and may not generalize to every person.
- Siri and Brozek conversions make different assumptions about fat-free tissue density.
- Skinfolds do not directly measure visceral fat and are not equivalent to DXA.
For another relevant cross-check, continue with the FFMI Calculator. Scale derived fat-free mass to height.
Frequently asked questions
Can I substitute a different skinfold site?
No. Each published equation requires the named sites.
Why do Siri and Brozek differ?
They convert body density using different assumptions about fat and fat-free tissue density.
Is 7-site always more accurate than 3-site?
Not automatically. Operator skill, site placement, and population fit can matter more than site count.
How many measurements should I take?
Follow your protocol, commonly repeating each site until readings are acceptably consistent rather than accepting one rushed measurement.
Can I compare this with a smart scale or DXA?
You can compare methods descriptively, but do not treat different measurement methods as interchangeable.
Primary sources and evidence limits
- Jackson and Pollock (1982): Generalized body-composition equations for adults
- Pollock et al. (1976): Body-density prediction in men
- Jackson, Pollock and Ward (1980): Generalized equations for women
Sources were checked 2026-10-04. They establish the published method or measurement context; they do not turn an anthropometric estimate into a diagnosis, direct body-composition measurement, or treatment recommendation.