Skinfold Body Fat Calculator
Calculate body fat percentage with the Jackson-Pollock 3-site and 7-site formulas, Durnin & Womersley and Petroski — using the same equations as Fitney's assessments.
About the protocols
Jackson-Pollock 3-site: men measure chest, abdomen and thigh; women measure triceps, suprailiac and thigh. The sum goes into a body density equation that also accounts for age. It is the most popular protocol in gyms because it is fast.
Jackson-Pollock 7-site: adds chest, midaxillary, triceps, subscapular, abdominal, suprailiac and thigh, for both men and women. More sites give a fuller picture of subcutaneous fat.
Durnin & Womersley: adds biceps, triceps, subscapular and suprailiac and uses a logarithmic equation with different coefficients per age band (under 17, 17–19, 20–29, 30–39, 40–49 and 50+).
Petroski: an equation validated on Brazilian adults, adding triceps, subscapular, suprailiac and medial calf.
All of these protocols estimate body density, which is then converted to body fat percentage. Fitney uses the Brožek equation by default; Siri gives slightly different numbers (up to 1–2 percentage points: a bit higher at high body fat, a bit lower in lean people). Pick one and keep it for future assessments.
How to measure each skinfold
Always measure on the right side of the body, with the person standing and relaxed. Pinch skin and fat between thumb and index finger about 1 cm above the site, apply the caliper and read it after 2–3 seconds. Take 3 measurements at each site, rotating between sites, and use the average (if two readings differ by more than 1–2 mm, measure again).
- Chest: diagonal fold, halfway between the anterior axillary line and the nipple (men) or one third of that distance from the armpit (women).
- Midaxillary: vertical fold on the midaxillary line, level with the xiphoid process.
- Triceps: vertical fold on the back of the upper arm, midway between the acromion and the olecranon, with the arm relaxed.
- Subscapular: diagonal fold (about 45°), 2 cm below the inferior angle of the shoulder blade.
- Abdominal: vertical fold about 2 cm to the right of the navel.
- Suprailiac: diagonal fold just above the iliac crest, on the anterior axillary line.
- Thigh: vertical fold on the front of the thigh, midway between the inguinal crease and the top of the kneecap, with the weight on the other leg.
- Biceps: vertical fold on the front of the upper arm, at the same level as the triceps site.
- Medial calf: vertical fold on the inner side of the lower leg, at the level of the largest calf circumference.
Frequently asked questions
Which skinfold protocol should I use?
For most adults, the Jackson-Pollock 3-site formula is the go-to choice: it is quick and reliable. The 7-site formula is better when you want more precision or when fat is unevenly distributed. Durnin & Womersley is handy if you already measure biceps and triceps, and Petroski was developed on a Brazilian adult population. Most importantly, stick to the same protocol so progress is comparable.
What is the difference between the 3-site and 7-site Jackson-Pollock formulas?
Both come from Jackson & Pollock. The 3-site version measures only three points (chest, abdomen and thigh for men; triceps, suprailiac and thigh for women), so it is faster. The 7-site version adds up chest, midaxillary, triceps, subscapular, abdominal, suprailiac and thigh, capturing trunk and limb fat more completely. For people with typical fat distribution the results are usually close.
Are skinfolds more accurate than bioimpedance (BIA)?
Done by a trained assessor with a good caliper, skinfolds typically have an error of about 3 to 4 percentage points and are barely affected by hydration. BIA is convenient but swings with water intake, meals and exercise that day. For tracking progress, any method works as long as you use the same one under the same conditions.
Which skinfold caliper should I buy?
Go for a professional caliper with constant jaw pressure of about 10 g/mm² and 0.1–0.2 mm resolution (e.g. Harpenden or Lange). Plastic calipers are fine for self-tracking, but they are less precise and less repeatable.
Complete body composition assessments in Fitney
In the app, every skinfold assessment is saved to your client's history, with progress charts and a PDF report with your brand. 14-day free trial.
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