What is the Jackson-Pollock Caliper Body Fat Calculator?
This tool estimates your body fat percentage from three skinfold caliper measurements using the widely published Jackson-Pollock 3-site equations. It first computes body density from the sum of the skinfolds and your age, then converts that density to a fat percentage with the Siri equation. It is a universal physiology calculation and is not specific to any country.
How to use it
Select your gender and enter your age in years. Then measure three skinfold sites with a caliper. For men, the sites are chest, abdomen and thigh. For women, the sites are triceps, suprailiac and thigh. Enter each reading and choose its unit (mm or cm). The calculator converts everything to millimetres, sums them, and returns your body density and estimated body fat percentage.
The formula explained
For men: $$BD = 1.10938 - 0.0008267\cdot S + 0.0000016\cdot S^2 - 0.0002574\cdot \text{age}.$$ For women: $$BD = 1.0994921 - 0.0009929\cdot S + 0.0000023\cdot S^2 - 0.0001392\cdot \text{age},$$ where \(S\) is the sum of the three skinfolds in millimetres. The Siri equation then gives $$\text{BodyFat\%} = \frac{495}{BD} - 450.$$
Worked example
A 30-year-old man with skinfolds of 15 mm, 18 mm and 20 mm has \(S = 53\) mm and \(S^2 = 2809\). $$BD = 1.10938 - 0.0008267\times 53 + 0.0000016\times 2809 - 0.0002574\times 30 = 1.0623372 \text{ g/cm}^3.$$ $$\text{BodyFat\%} = \frac{495}{1.0623372} - 450 \approx 16.0\%.$$
FAQ
How accurate is it? Skinfold methods estimate body fat within a few percent when technique is consistent. It is not a clinical measurement.
Where do I measure? Take readings on the right side of the body at the mid-point of each pinch.
Is this valid at any age? The regression is validated roughly for ages 18-70; outside this range results are extrapolations.
