Turn body fat caliper readings into body density, body fat percentage, fat mass and lean mass using the Jackson-Pollock 3, 4 and 7-site equations or the Durnin-Womersley 4-site method.
Last updated:
Method
Sex
years
Weight unit
Skinfold readings (mm, right side of the body)
mm
Diagonal fold halfway between armpit and nipple (men); one third of the way for women
mm
Vertical fold 2 cm to the right of the navel
mm
Vertical fold on the front of the thigh, midway between hip and knee
mm
Vertical fold on the back of the upper arm, midway between shoulder and elbow
mm
Diagonal fold just above the front of the hip bone
mm
Diagonal fold just below the shoulder blade
mm
Vertical fold on the side of the torso, level with the bottom of the breastbone
mm
Vertical fold on the front of the upper arm, midway up
Enter your values to see the result.
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How to use the Skinfold Body Fat Calculator
Choose a method: 3-site is quickest, 7-site uses more of the body, Durnin-Womersley uses the arms and back.
Enter your sex, age and body weight.
Take each skinfold on the right side, two or three times, and enter the average in millimeters.
Read your body fat, density, fat mass and lean mass.
Re-measure every few weeks with the same method and the same person taking the readings.
BD = c − m · log₁₀(S), with c and m chosen by sex and age group (17–19, 20–29, 30–39, 40–49, 50+)
S is the sum of the skinfolds in millimeters and BD is body density in g/cm³. Body fat is then %BF = 495 ÷ BD − 450 (Siri, 1961).
Tips for reliable caliper readings
Measure on the right side of the body, standing upright with muscles relaxed.
Mark each site with a skin pen so you measure the same spot every time.
Take at least two readings per site and use the average; take a third if they differ by more than 2 mm.
Measure at the same time of day, before exercise and when normally hydrated.
Track the sum of skinfolds as well as body fat %: if the sum goes down, you have lost fat at those sites regardless of the equation.
Cheap plastic calipers are fine for tracking trends; spring calipers with constant pressure are more repeatable.
Frequently asked questions
How do you calculate body fat from skinfolds?
Add up the skinfold readings in millimeters, put the sum and your age into a body density equation such as Jackson-Pollock or Durnin-Womersley, then convert density to body fat with the Siri equation: %BF = 495 ÷ density − 450.
Which skinfold method is most accurate?
With a skilled tester, skinfold methods usually estimate body fat within about 3 to 4 percentage points of laboratory methods. The 7-site Jackson-Pollock test samples more of the body, but the 3-site version gives very similar results. Consistent technique matters more than the method.
Where are the Jackson-Pollock 3-site locations?
For men: chest, abdomen and thigh. For women: triceps, suprailiac (just above the hip bone) and thigh. All folds are taken on the right side of the body while standing relaxed.
What is the Durnin-Womersley method?
Published in 1974, it uses four skinfolds (biceps, triceps, subscapular and suprailiac) and age- and sex-specific constants: body density = c − m × log10(sum of skinfolds). It is often used in research and clinical settings.
How do I take a skinfold measurement correctly?
Pinch a double fold of skin and fat between thumb and finger about 1 cm above the site, place the caliper jaws on the site, read the dial after 1 to 2 seconds, and repeat until two readings agree within 1 to 2 mm. Do not measure right after exercise or a shower.
What is the difference between the Siri and Brozek equations?
Both convert body density to body fat percentage, assuming fixed densities for fat and fat-free tissue. Siri uses %BF = 495 ÷ BD − 450 and Brozek uses %BF = 457 ÷ BD − 414.2. They give results within about one percentage point of each other for most people.
Are all the tools on FreeToolCabin tested for quality and accuracy?
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