Calculate estimated body fat percentage from Jackson-Pollock 3-site skinfold measurements in mm and age for men or women, with fitness category.
Disclaimer: This calculator provides an estimate (not a medical diagnosis) using sex-specific 3-site skinfold equations and the Siri conversion. Results can be inaccurate depending on technique, device, age, sex, and body type. Not intended for children/teens, pregnancy, or people with a history of eating disorders without clinician guidance. If you’re concerned about your health or weight, consult a licensed clinician.
- Measure on the same side of the body each time (commonly the right side).
- Take 2–3 readings per site and use the average.
- Pinch the skinfold firmly, place the caliper jaws correctly, and read after a consistent delay (per your caliper’s instructions).
- Re-check your selected units (mm/cm/in) before calculating.
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Body Fat Caliper Formula
The body fat caliper calculator uses the Jackson-Pollock 3-site skinfold equations to estimate body density, then converts body density to body fat percentage with the Siri equation.
Men
S = chest + abdomen + thigh
D = 1.10938 - 0.0008267*S + 0.0000016*S^2 - 0.0002574*A
Women
S = triceps + suprailiac + thigh
D = 1.0994921 - 0.0009929*S + 0.0000023*S^2 - 0.0001392*A
Body Fat Percentage
BF = 495/D - 450
- S = sum of the 3 skinfold measurements, in millimeters
- A = age, in years
- D = estimated body density, in g/cm³
- BF = estimated body fat percentage
The men’s mode adds the chest, abdomen, and thigh skinfolds, then applies the men’s Jackson-Pollock density equation. The women’s mode adds the triceps, suprailiac, and thigh skinfolds, then applies the women’s equation. After body density is found, the same Siri equation converts density into estimated body fat percentage. The category shown with the result is based on the final body fat percentage, not on a separate formula.
Skinfold Sites and Body Fat Categories
Use the correct 3-site set for the selected sex. All skinfold values should be entered in millimeters.
| Mode | Site 1 | Site 2 | Site 3 | Age range accepted |
|---|---|---|---|---|
| Men | Chest | Abdomen | Thigh | 18 to 80 years |
| Women | Triceps | Suprailiac | Thigh | 18 to 80 years |
| Category | Men | Women |
|---|---|---|
| Essential fat | Less than 6% | Less than 14% |
| Athletic | 6% to less than 14% | 14% to less than 21% |
| Fitness | 14% to less than 18% | 21% to less than 25% |
| Average | 18% to less than 25% | 25% to less than 32% |
| Above average | 25% or higher | 32% or higher |
Examples
Example 1: Men
Suppose your measurements are chest 12 mm, abdomen 24 mm, thigh 18 mm, and age 35.
S = 12 + 24 + 18 = 54 mm
D = 1.10938 - 0.0008267*54 + 0.0000016*54^2 - 0.0002574*35 = 1.06039
BF = 495/1.06039 - 450 = 16.8%
The estimated body fat is about 16.8%, which falls in the fitness category for men.
Example 2: Women
Suppose your measurements are triceps 18 mm, suprailiac 15 mm, thigh 22 mm, and age 30.
S = 18 + 15 + 22 = 55 mm
D = 1.0994921 - 0.0009929*55 + 0.0000023*55^2 - 0.0001392*30 = 1.04766
BF = 495/1.04766 - 450 = 22.5%
The estimated body fat is about 22.5%, which falls in the fitness category for women.
FAQ
How accurate is a body fat caliper estimate?
A caliper estimate is useful for tracking trends, but it is not a perfect measurement of body fat. Accuracy depends on consistent technique, correct site location, caliper quality, and the person taking the measurements. For best tracking, measure the same sites the same way each time and compare changes over time rather than treating one result as exact.
Should you take one measurement or several?
Take at least two measurements at each site. If the values are not close, take a third measurement and use the average. Avoid measuring immediately after exercise, because changes in fluid and skin temperature can affect the skinfold reading.
Why does age affect the result?
The Jackson-Pollock equations include age because the relationship between skinfold thickness, body density, and body fat percentage changes with age. Two people with the same skinfold sum can receive slightly different estimates if their ages are different.
