Skinfold assessment is still the most common way personal trainers and nutritionists estimate body fat: it’s cheap, fast and, done well, very reliable for tracking progress. The best-known protocol is Jackson-Pollock, in its 3-site and 7-site versions.
If you just want the result, use our skinfold calculator. If you want to understand the protocol, read on.
3-site protocol: which sites to measure
| Men | Women |
|---|---|
| Chest | Triceps |
| Abdomen | Suprailiac |
| Thigh | Thigh |
It’s the most practical protocol: three measurements per assessment, a few minutes per client.
7-site protocol: which sites to measure
The same sites for men and women:
- Chest
- Midaxillary
- Triceps
- Subscapular
- Abdomen
- Suprailiac
- Thigh
Because it covers more of the body, the 7-site version tends to be more stable for people who store fat unevenly (a lot on the abdomen and little on the limbs, for example).
How to measure each site
- Chest: diagonal fold, halfway between the anterior axillary line and the nipple (men).
- Midaxillary: vertical fold on the midaxillary line, level with the xiphoid process.
- Triceps: vertical fold on the back of the arm, midway between the acromion and the olecranon.
- Subscapular: diagonal fold just below the inferior angle of the scapula.
- Abdomen: 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 patella.
Best practices
- Always measure on the right side, with the client standing and relaxed.
- Pinch the fold with your thumb and index finger, place the caliper about 1 cm below your fingers and read after 2–3 seconds.
- Take two measurements per site and use the average; if they differ by more than 1–2 mm, take a third.
- Avoid measuring right after training, on sweaty skin or when the client is dehydrated.
- On reassessments, keep the same assessor, the same caliper and the same time of day. Consistency matters more than the absolute number.
From millimeters to body fat percentage
The calculation has two steps:
- The sum of skinfolds goes into the Jackson-Pollock body density equation, which also uses sex and age.
- Density is converted to body fat percentage with the Siri or Brozek equation. The two can differ by 1–2 percentage points (Siri reads higher at high body fat and lower in lean people), so pick one and keep it across reassessments.
With the client’s weight you also get fat mass and lean mass in kg, which tend to motivate more than the percentage alone: “you gained 1.2 kg of lean mass” makes for a great reassessment conversation.
3 or 7 sites: which one to choose?
- 3 sites: day-to-day coaching, frequent reassessments and clients with a typical fat distribution.
- 7 sites: a more complete first assessment, athletes and clients with fat concentrated in specific areas.
The most important rule is not to switch protocols between assessments of the same client. Comparisons only make sense with the same method.
Fitness assessments in the app
In Fitney, you enter the skinfolds and the app automatically calculates body fat percentage, lean mass, fat mass and BMI. Several protocols are available (Jackson-Pollock 3 and 7 sites, Durnin-Womersley, Petroski, Guedes and others). Every assessment generates progress charts and can be exported as a PDF.
Read the complete fitness assessment guide and see Fitney’s fitness assessments, with 14 days free, no credit card.
