π Skinfold Body Fat Calculator
Jackson-Pollock 3-site body fat estimate.
For informational purposes only, not medical advice. Consult a healthcare professional.
The Jackson-Pollock 3-site method estimates body density from three skinfold thicknesses, then converts density to body fat percentage with the Siri equation. It is the most validated field method short of a DXA scan: trained testers land within a few percentage points of lab measures. Men measure chest, abdomen, and thigh; women measure triceps, suprailiac, and thigh, because fat distributes differently by sex. This calculator runs the sex-specific equations with age correction.
How to Use This Calculator
Pick sex for the correct 3 sites, enter age, and enter the three caliper readings in millimeters. The calculator runs the Jackson-Pollock equation.
Measure each site with calipers: pinch the fold, wait 2 seconds, read in mm. Take each site twice and average.
Enter the three sites for your sex: men use chest, abdomen, thigh; women use triceps, suprailiac, thigh.
Read the body fat percent with the category. Consistent technique matters more than perfect technique for tracking.
How the Math Works
Sum the three skinfolds in millimeters. For men, density equals 1.10938 minus 0.0008267 times the sum plus 0.0000016 times the sum squared minus 0.0002574 times age. For women, density equals 1.0994921 minus 0.0009929 times the sum plus 0.0000023 times the sum squared minus 0.0001392 times age. Body fat percent is 495 divided by density minus 450, the Siri equation. A 30-year-old man with skinfolds summing to 45 mm gets density about 1.0677 and body fat about 13.6 percent. The age term accounts for fat redistributing inward with age at the same skinfold sum.
Worked Example
A 30-year-old man with chest 12 mm, abdomen 20 mm, and thigh 13 mm has a skinfold sum of 13.6%%, giving body density 1.0677 g/cc and body fat of 13.6 %% body fat. The calculator places this in the Athletic band. The abdomen fold dominates the sum, which is typical: central sites carry the most information about total fat in men.
Reading Your Result
For men, under 8 percent is very lean, 8 to 14 athletic, 15 to 20 fit, 21 to 24 average, over 24 high. For women, under 14 very lean, 14 to 20 athletic, 21 to 26 fit, 27 to 31 average, over 31 high. Use the number for tracking: remeasure monthly with the same tester and technique, and watch the trend rather than worshipping a single reading. If calipers are not available, waist-based estimators on this site give a rougher alternative.
| Men | Women | Category |
|---|---|---|
| Under 8%% | Under 14%% | Very lean |
| 8-20%% | 14-26%% | Athletic to fit |
| 21-24%% | 27-31%% | Average |
| Over 24%% | Over 31%% | High |
Limitations
Accuracy depends on tester skill: beginners err by 5+ points, trained testers by 2 to 3. Very lean and very obese extremes challenge the equations. Hydration shifts skinfold compressibility slightly. It estimates total fat, not visceral distribution, and cannot replace medical body-composition assessment where precision matters.
Related Calculators
Related tools: relative fat mass calculator BMI calculator body fat percentage calculator.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
How do you measure skinfolds?
Pinch the skin and fat away from the muscle with thumb and forefinger, apply the caliper about 1 cm from the fingers, wait 2 seconds, and read in millimeters. Measure each site twice and average. All measurements go on the right side of the body by convention.
Where are the 3 sites for men?
Chest: diagonal fold midway between armpit and nipple. Abdomen: vertical fold 2 cm right of the navel. Thigh: vertical fold on the front mid-thigh. Sum the three in millimeters.
Where are the 3 sites for women?
Triceps: vertical fold on the back of the upper arm midway. Suprailiac: diagonal fold above the hip bone. Thigh: vertical fold on the front mid-thigh. Sum the three in millimeters.
How accurate are skinfold calipers?
Within 2 to 4 percentage points of DXA with a trained tester, worse with beginners. The equations themselves are well validated; nearly all the error is technique. Same tester, same caliper, same time of day gives the best tracking.
What is the Siri equation?
Body fat percent equals 495 divided by body density minus 450. It converts the density estimated from skinfolds into a fat percentage using assumed densities of fat and lean tissue. The Brozek equation is a close alternative.
Do I need expensive calipers?
Decent plastic calipers work for tracking if used consistently; professional metal calipers are more precise and durable. The bigger investment is learning technique: a skilled tester with cheap calipers beats a novice with expensive ones.
Can I measure my own skinfolds?
Some sites yes, like the thigh, but chest, triceps, and suprailiac are hard to pinch and read solo without distorting the fold. A partner or trainer gets better numbers. Self-measurement works best for tracking rough trends.
Why does age matter in the formula?
Because at the same skinfold thickness, older adults carry more internal fat. The age term corrects for this redistribution so the estimate stays honest across decades. Ignoring age understates fat in older adults.
Skinfold vs BMI: which is better?
Skinfold estimates body fat directly while BMI infers it from weight and height, so skinfold wins for muscular or unusual builds. BMI wins on simplicity and massive validation data. Together they cross-check each other well.
How often should I remeasure?
Every 4 to 8 weeks. Fat changes slowly and measurement noise is real, so weekly remeasuring mostly charts technique variation. Pair it with waist measurements and progress photos for the full picture.