Skinfold Body Fat Calculator

Which skinfold equation does the calculator use?

The Jackson-Pollock 3-site equations for body density, followed by the Siri equation, body fat % = 495 ÷ density − 450. For men the density is 1.10938 − 0.0008267 × S + 0.0000016 × S² − 0.0002574 × age. For women it is 1.0994921 − 0.0009929 × S + 0.0000023 × S² − 0.0001392 × age. S is the sum of the three skinfolds in millimetres.

Which three sites do I enter, and in which fields?

For men: chest in Site 1, abdomen in Site 2 and thigh in Site 3. For women: triceps in Site 1, suprailiac in Site 2 and thigh in Site 3. Using the wrong site set gives an answer that looks plausible but belongs to a different equation, so check the gender selection first.

How is each skinfold taken?

The usual descriptions are a diagonal chest fold between the armpit and nipple, a vertical abdominal fold about 2 cm beside the navel, a vertical thigh fold midway between hip and knee, a vertical triceps fold at the back-of-arm midpoint and a diagonal suprailiac fold above the hip bone. Measure the same side each time, pinch skin and fat but not muscle, and enter millimetres.

What does the age limit do?

The age you enter is held between 18 and 100 for the calculation. A 16-year-old is therefore treated as 18, and the equations are intended for adults. Age enters the density equation directly, so the same skinfold sum gives a somewhat different body-fat figure at different ages.

How are the categories assigned?

By fixed cut-offs on the body fat %. Men: below 5% Essential fat, up to 13% Athletic, up to 17% Fitness, up to 24% Average and above that Obese. Women: below 14% Essential fat, up to 20% Athletic, up to 24% Fitness, up to 31% Average and above that Obese. They are classification labels in the tool, not diagnoses, and they ignore age and ethnicity.

How accurate is the estimate?

It is a regression estimate from a caliper, so it depends on measurement technique, the caliper, the person measuring and hydration. Small differences in where the fold is taken can shift the answer by a percentage point or more. Take each site two or three times, average them, and compare only readings taken the same way. A single reading is not a diagnosis.

What happens with zero or missing measurements?

All three skinfolds must be above 0 mm, or the calculator shows an error rather than a body fat figure. The calculation also floors the result at 0%. It does not check whether your entries are physically plausible, so a typo such as 150 instead of 15 mm will be computed.