Skinfold Body Fat Calculator

The Jackson-Pollock 3-site skinfold method estimates body-fat percentage from caliper measurements at three sites. By measuring the fat layer just under the skin, it predicts overall body density and converts that to a body-fat figure — a fast, low-cost technique that is accurate to within about 3-4% when done with good technique.

The Formula

Sex-specific equations predict body density from the sum of three skinfolds (mm) and age, then the Siri equation converts density to body-fat percentage. Men measure chest, abdomen, and thigh; women measure triceps, suprailiac, and thigh.

S is the sum of the three skinfolds in millimetres.

Worked Example

A 30-year-old man with chest 12 mm, abdomen 18 mm, thigh 15 mm (sum = 45 mm):

• D = 1.10938 − 0.0008267×45 + 0.0000016×45² − 0.0002574×30
• D ≈ 1.10938 − 0.0372 + 0.0032 − 0.0077 = 1.0676
• Body fat = 495 / 1.0676 − 450 ≈ 13.7% → Athletes range

Body-Fat Categories

Measuring Well

• Pinch the skinfold firmly, place the caliper 1 cm from your fingers, and read after 1-2 seconds.
• Take all readings on the right side of the body.
• Measure each site twice and average; if readings differ by more than 1-2 mm, take a third.

Note: Skinfold estimates depend heavily on caliper technique and site location. This is an informational body-composition tool, not a clinical measurement. For medical assessment, consult a qualified professional.