Estimate body fat from protocol-based skinfold sites
Choose the protocol, enter age and sex, then fill the required caliper sites in millimetres. Add body weight when you want fat mass and lean mass as well as the body fat percentage estimate.
Measurement reminder
Use the same protocol each time, measure the same side of the body, and average two or three repeated readings per site. Skinfold estimates are highly technique-sensitive, so a consistent trend is more useful than one isolated percentage.
Required site guide
Jackson-Pollock 3-site uses these 3 skinfold sites for male mode.
Chest Diagonal fold
Diagonal fold halfway between the anterior axillary line and nipple.
Abdomen Vertical fold
Vertical fold about 2 cm to the right of the navel.
Thigh Vertical fold
Vertical fold on the front of the thigh, midway between hip and knee.
Result
13.6%
Jackson-Pollock 3-site estimate for men aged 30.
Athletic
Sum of sites
45 mm
Body density
1.0677 g/mL
Required sites
3
10.9 kg / 24 lb
Estimated fat mass
69.1 kg / 152.3 lb
Estimated lean mass
Protocol
Jackson-Pollock 3-site
Sex
Male
Age
30 years
Site checklist
Chest, Abdomen, Thigh
Measurement technique
Average 2-3 readings per site; keep assessor, side, and caliper consistent
Tracking note
Use the same protocol, the same side of the body, and average two or three readings per site when tracking progress over time.
Skinfold measurements require trained technique to be accurate. Results depend on calliper calibration, site location, and measurement consistency. For clinical body composition assessment, consult a qualified assessor.
Skinfold caliper measurements are one of the most widely used field methods for estimating body fat percentage. By measuring the thickness of subcutaneous fat at standardised sites, validated equations convert these measurements into a body density estimate, from which body fat percentage is derived.
How skinfold measurements work
A skinfold caliper measures the thickness of a double fold of skin and subcutaneous fat at specific anatomical sites. The sum of multiple sites correlates strongly with total body fat when measured consistently by a trained assessor. This calculator supports three established protocols: Jackson-Pollock 3-site, Jackson-Pollock 7-site, and Durnin-Womersley 4-site.
Body density is calculated from the site sum using the protocol-specific equation. Body fat percentage is then derived from density using the Siri formula: %fat = (4.95/density − 4.50) × 100. Different protocols use different site combinations and regression equations validated in different populations.
Body density = protocol-specific equation using skinfold sum and age
Jackson-Pollock equations use sex-specific polynomial terms; Durnin-Womersley uses log10 of the four-site skinfold sum.
Body fat % = (4.95 / body density − 4.50) × 100
The Siri equation converts estimated body density into estimated body fat percentage.
Fat mass = body weight × body fat %
When body weight is entered, the calculator converts the body fat percentage into estimated fat mass and lean mass.
Choosing Jackson-Pollock 3-site, Jackson-Pollock 7-site, or Durnin-Womersley
The Jackson-Pollock 3-site method is the fastest skinfold body fat calculator workflow. In male mode it uses chest, abdomen, and thigh. In female mode it uses triceps, suprailiac, and thigh. It is useful when you want a quick caliper estimate and can keep the same assessor and sites consistent over time.
The Jackson-Pollock 7-site protocol uses chest, abdomen, thigh, triceps, subscapular, suprailiac, and midaxillary readings. It takes longer, but it gives a broader picture of subcutaneous fat distribution and is often preferred by coaches or trainers who already know how to locate each site.
Durnin-Womersley uses biceps, triceps, subscapular, and suprailiac skinfolds. It is a useful comparison method because the equation was built around four upper-body sites and age-group coefficients, but it can produce a different answer from Jackson-Pollock even when the measurements are technically good.
How to measure each skinfold site more consistently
Use millimetres exactly as read from the caliper. A practical field routine is to measure on the same side of the body, mark or locate the same anatomical point each time, pull the skinfold away from the underlying muscle, place the caliper at the fold, and record the reading after the caliper settles. The live calculator now shows a short site cue for each required site so the protocol is easier to follow.
Take two or three readings at each site and use the average or the closest repeated values when they agree. Large differences between repeated readings usually mean the site location, pinch, or caliper angle changed. In that case, repeat the site before trusting the percentage.
Chest: diagonal fold halfway between the anterior axillary line and nipple.
Abdomen: vertical fold about 2 cm to the right of the navel.
Thigh: vertical fold on the front of the thigh, midway between hip and knee.
Triceps and biceps: vertical folds at the midpoint of the upper arm.
Subscapular, suprailiac, and midaxillary sites require careful landmarking; poor placement can shift the final estimate.
Worked example: Jackson-Pollock 3-site for a male measurement set
Suppose a 30-year-old man has skinfold readings of chest 10 mm, abdomen 20 mm, and thigh 15 mm. The site sum is 45 mm. Using the Jackson-Pollock 3-site male equation, the calculator derives body density first and then converts that density to body fat percentage with the Siri formula.
That sequence is why repeated site technique matters more than any single reading in isolation. If the same assessor repeats the same three sites consistently, the result is much more useful for trend tracking even when the absolute body fat percentage is only an estimate.
Using body weight for fat mass and lean mass
Body fat percentage is easier to act on when it is translated into estimated fat mass and lean mass. If a result is 13.6% body fat at 80 kg, estimated fat mass is about 10.9 kg and estimated lean mass is about 69.1 kg. That split is still an estimate, but it gives more practical context than a percentage alone.
This is why the calculator includes body weight as an optional input. The skinfold equation itself does not need body weight, so you can leave weight blank and still get body fat percentage. Add weight only when you want the body composition breakdown.
Accuracy, reliability, and when not to over-read the result
Skinfold testing can be a useful field method, but it is not a clinical scan. It estimates subcutaneous fat and then uses population equations to infer body density and body fat percentage. Technique, caliper quality, assessor experience, hydration, and body-fat distribution all affect the result.
For trend tracking, consistency matters more than chasing an exact percentage. Compare results only when the protocol, assessor, caliper, time of day, and measurement side are broadly the same. If you switch from a 3-site skinfold test to a 7-site skinfold test, Durnin-Womersley, Navy circumference, BIA scale, or DXA scan, expect the number to change even if your body composition has not changed much.
The Jackson-Pollock 3-site is the most practical for field testing — three measurements are quick and sufficient for most purposes. The 7-site provides greater accuracy at the cost of complexity. The Durnin-Womersley protocol uses upper-body sites and was validated in a broad age range (17–72 years). Use the same protocol consistently across measurements to track changes over time.
How often should I repeat each skinfold site?
A common field approach is to measure each site two or three times and use the average or the closest two values when they agree closely. Repeating the site reduces the chance that a single pinch or placement error distorts the estimate.
Why can different protocols give different body fat percentages?
Each protocol uses a different set of sites and a different regression equation. They were validated in different populations, so the same person can get slightly different results depending on whether you use Jackson-Pollock 3-site, Jackson-Pollock 7-site, or Durnin-Womersley.
Can I compare today’s result with an older result from another protocol?
Trend comparisons are most reliable when you keep the same protocol, the same assessor, and the same site technique each time. Switching protocols can change the estimate even if body composition has not changed very much.
What is the difference between a 3-site and 7-site skinfold calculator?
A 3-site skinfold calculator is faster and uses sex-specific sites. Jackson-Pollock 7-site uses seven readings for both male and female mode, so it takes longer but gives a broader distribution check. The 7-site method can be more useful for trained assessors, athletes, or people tracking changes closely.
Do I need body weight for a skinfold body fat calculation?
No. The body fat percentage estimate comes from age, sex, protocol, and skinfold millimetres. Body weight is optional and is only used to split the percentage into estimated fat mass and lean mass.
Should I average multiple skinfold readings?
Yes. Measure each required site two or three times and use the average or the closest repeated values when they agree. Repeated measurements reduce the chance that one bad pinch, site placement, or caliper angle controls the result.
Is a skinfold calculator better than the Navy body fat calculator?
They answer similar body-composition questions with different field methods. Skinfold uses caliper measurements at anatomical sites, while Navy-style calculators use tape-measure circumferences. Skinfold can be useful when a trained assessor is available; the Navy method is easier for most home users.
How accurate is a skinfold body fat percentage estimate?
Accuracy depends on the assessor, caliper, site selection, and population fit of the equation. Even with good technique, treat the answer as an estimate and focus on repeatable trends rather than a single exact percentage point.
