Energy calculator
Skinfold Body Fat Calculator (Caliper, 3 and 7 Site)
Estimate body fat percentage from caliper skinfold readings with the Jackson-Pollock 3-site or 7-site equations, with the sum, density and formula shown.
Estimated body fat
15.1%
Estimated fat mass: 27.15 lb · Estimated lean body mass: 152.85 lb
Jackson-Pollock 3-site equation for men: chest, abdomen, thigh
Sum = 10 + 25 + 15 = 50 mmDensity = 1.10938 − 0.0008267 × 50 + 0.0000016 × 50² − 0.0002574 × 30 = 1.0643 g/mlBody fat = 495 ÷ 1.0643 − 450 = 15.1%The result uses unrounded values. Density is rounded to four decimals and body fat to one decimal for display.
An estimate from skinfold readings and age. In the men’s study the typical error was about 3.5 body fat percentage points, and results depend on who takes the readings.
How this skinfold body fat calculator works
This skinfold body fat calculator estimates your body fat percentage from caliper readings with the Jackson-Pollock equations. Choose 3-site or 7-site, enter each skinfold in millimeters as your caliper shows it, and add your sex and age. The result is shown to one decimal place, with the sum of your skinfolds, your estimated body density, and the substituted formula under it.
Weight is optional. The equations do not use it. If you enter it, the page also shows estimated fat mass and lean body mass, worked out from the body fat percentage.
The Jackson-Pollock 3-site and 7-site equations
Each equation turns the sum of your skinfolds (S, in mm) and your age (A, in years) into body density in grams per milliliter. The men’s equations come from Jackson and Pollock (1978), and the women’s from Jackson, Pollock, and Ward (1980).
Men, 7-site: density = 1.112 − 0.00043499 × S + 0.00000055 × S² − 0.00028826 × A
Men, 3-site: density = 1.10938 − 0.0008267 × S + 0.0000016 × S² − 0.0002574 × A
Women, 7-site: density = 1.097 − 0.00046971 × S + 0.00000056 × S² − 0.00012828 × A
Women, 3-site: density = 1.0994921 − 0.0009929 × S + 0.0000023 × S² − 0.0001392 × A
Density falls as the sum rises and as age rises. The squared term bends the curve, so each extra millimeter lowers density a little less than the one before. At a very high sum the curve turns, and body fat would start to fall as skinfolds grow, so the page gives no number once the sum reaches about 395.4 mm for men’s 7-site, 258.3 mm for men’s 3-site, 419.4 mm for women’s 7-site, or 215.8 mm for women’s 3-site.
From body density to body fat percentage
Body fat % = 495 ÷ density − 450
This is the Siri equation, the conversion Jackson and Pollock used. Some calculators use the Brozek equation instead. For the examples on this page the two results are less than one percentage point apart. This page shows the Siri result only.
Where to take each skinfold
Men’s 3-site uses chest, abdomen, and thigh. Women’s 3-site uses triceps, suprailiac, and thigh. Both 7-site equations use all seven sites: chest, midaxillary, triceps, subscapular, abdomen, suprailiac, and thigh.
Chest: a diagonal fold half of the way from the front of the armpit to the nipple for men, a third of the way for women. Midaxillary: a vertical fold on the line down the middle of the armpit, level with the bottom tip of the breastbone. Triceps: a vertical fold on the back of the upper arm, halfway between the shoulder and the elbow, with the arm relaxed.
Subscapular: a fold angled at about 45 degrees, 1 to 2 cm below the lower tip of the shoulder blade. Abdomen: a vertical fold 2 cm to the side of the navel. Suprailiac: a diagonal fold just above the top of the hip bone, in line with the front of the armpit. Thigh: a vertical fold on the front of the thigh, midway between the hip crease and the top of the kneecap.
Measure on the right side and take at least two readings at each site. If two readings differ by more than 10%, take that site again. Rotate through the sites rather than repeating one site in a row, and do not measure right after exercise. Sources describe the suprailiac site in more than one way, so use the same spot every time.
Skinfold examples
A 30-year-old man with chest 10, abdomen 25, and thigh 15 mm has a 3-site sum of 50 mm. Density is 1.10938 − 0.0008267 × 50 + 0.0000016 × 50² − 0.0002574 × 30 = 1.0643, and body fat is 495 ÷ 1.0643 − 450, about 15.1%. At 180 lb, that is about 27.15 lb of fat mass and 152.85 lb of lean body mass.
Adding midaxillary 12, triceps 10, subscapular 15, and suprailiac 15 mm gives him a 7-site sum of 102 mm and about 14.9%. A 30-year-old woman with triceps 18, suprailiac 15, and thigh 25 mm has a 3-site sum of 58 mm and about 23.5%. With chest 8, midaxillary 10, subscapular 14, and abdomen 20 mm added, her 7-site sum is 110 mm and the estimate is about 22.2%.
Age moves the result even when the skinfolds stay the same. At 50 instead of 30, the same readings give about 17.3% for his 3-site, 17.4% for his 7-site, 24.7% for her 3-site, and 23.4% for her 7-site.
Fat mass, lean mass, and other calculators
Fat mass is weight × body fat % ÷ 100, and lean body mass is weight minus fat mass. This page uses the same lean mass calculation as the body fat calculator and the FFMI calculator on this site.
The body fat calculator estimates body fat from tape measurements instead, with the Navy circumference method. The two methods can give different numbers for the same person. The FFMI calculator and the Katch-McArdle calculator both start from a body fat percentage, so you can enter the result from this page there.
Limits of the estimate
The equations were built by comparing skinfolds with underwater weighing. In the men’s study the typical error was about 3.5 body fat percentage points, and results depend heavily on who takes the readings and how.
The men’s study tested ages 18 to 61, 7-site sums of 32 to 272 mm, and 3-site sums of 14 to 118 mm. The women’s study tested ages 18 to 55. Outside those ranges the page labels the result a rough estimate. EVR found no published skinfold sum range for the women’s study, so women’s results get no sum label. Results below 2% or above 70% also show a warning to recheck the readings.
Other 3-site sets exist, such as chest, triceps, and subscapular for men. They use different equations, and this page does not include them.
Sources
Jackson AS, Pollock ML. Generalized equations for predicting body density of men. Br J Nutr. 1978;40(3):497–504. doi:10.1079/BJN19780152. PMID 718832.
Jackson AS, Pollock ML, Ward A. Generalized equations for predicting body density of women. Med Sci Sports Exerc. 1980;12(3):175–181. doi:10.1249/00005768-198023000-00009. PMID 7402053.
Body fat from density: Siri WE, 1961, as used by Jackson and Pollock (1978).
Site descriptions: Kravitz L, Heyward VH. Body Composition Assessment. University of New Mexico.
EVR read the men’s equations in the full 1978 paper. The full text of the 1980 paper was not available to EVR, so the women’s equations were checked against its published abstract and several later open-access papers that reprint them with the same digits.
Sources last checked: 9 October 2026.
Frequently asked questions
What is the Jackson-Pollock 3-site skinfold formula?
For men, density = 1.10938 − 0.0008267 × S + 0.0000016 × S² − 0.0002574 × age, with chest, abdomen, and thigh. For women, density = 1.0994921 − 0.0009929 × S + 0.0000023 × S² − 0.0001392 × age, with triceps, suprailiac, and thigh. S is the sum in mm, and body fat % = 495 ÷ density − 450.
Which sites does the 7-site skinfold test use?
Chest, midaxillary, triceps, subscapular, abdomen, suprailiac, and thigh, for both men and women. The men’s and women’s 7-site equations use the same seven sites with different numbers.
Should I use 3-site or 7-site?
Both come from the same studies and had similar error there. The 3-site test takes fewer readings. Use the same one each time so your results can be compared.
Why does the calculator ask for age?
Every equation includes age. With the same skinfolds, an older person gets a lower density and a higher body fat estimate. For a man with a 3-site sum of 50 mm, the estimate is about 15.1% at 30 and about 17.3% at 50.
Do I need to enter my weight?
No. Weight is not part of the equations. It is used only to show estimated fat mass and lean body mass, in the unit you choose.
Why is my result different from the tape-measure calculator?
Skinfold and tape-measure methods use different equations built on different groups of people, so they can give different numbers for the same person. Neither one measures body fat directly.
How accurate is a skinfold body fat estimate?
In the men’s study the typical error was about 3.5 body fat percentage points, and it depends heavily on who takes the readings. Take readings the same way each time, at the same sites, with the same caliper.