● Body composition

Body fat with skinfold calipers.

The Jackson-Pollock 3-site method uses skinfold measurements in mm to calculate body density and then body fat percentage — one of the most validated field tests.

📏

Body Fat — Skinfold Method

Jackson-Pollock 3-site: body density → body fat %

✏️

Your measurements

Units — skinfolds always in mm regardless

Sex

Age (years)

Chest skinfold — always mm

Abdomen skinfold — always mm

Thigh skinfold — always mm

Body weight — optional, for lean/fat mass

📊

Your results

— %

Body fat %

EssentialAthleteFitAverageObese

Sum of skinfolds—

Body densitySiri equation—

Body fat %—

Display · data-ad-format="auto"

How it's calculated

Body density from skinfolds, then fat % via the Siri equation

The Jackson-Pollock 3-site skinfold calculator measures subcutaneous fat at three body sites in millimetres, computes body density using a sex- and age-specific regression equation, and converts density to body fat percentage using the Siri equation: %BF = (495 ÷ density) − 450.

A trained technician uses a skinfold caliper to pinch and measure fat tissue at each site. The sum of the three measurements (ΣS) feeds into the Jackson-Pollock regression. Age is included because fat distribution shifts with age even when total fat remains constant.

Men: density = 1.10938 − 0.0008267×ΣS + 0.0000016×ΣS² − 0.0002574×age
Women: density = 1.0994921 − 0.0009929×ΣS + 0.0000023×ΣS² − 0.0001392×age
%BF = (495 ÷ density) − 450

1
Sum of 3 skinfold sites (mm)
—
2
Body density (g/mL) — sex- and age-specific regression
—
3
Body fat % = (495 ÷ density) − 450
—

Understand the terms

Skinfold caliper: An instrument that measures the thickness of a double fold of skin (plus underlying fat) at a specific body site, in millimetres.
Body density: The ratio of body mass to volume, in g/mL. Lean tissue is denser (~1.10 g/mL) than fat (~0.90 g/mL), so a denser body has less fat.
Siri equation: %BF = (495 ÷ density) − 450. A two-component model converting body density to fat percentage, published by William Siri in 1956.
Suprailiac site: The skinfold measured just above the iliac crest (hip bone), at a diagonal angle — commonly used for women.

See the full glossary →

Disclaimer: estimation tool for informational and planning purposes. The Jackson-Pollock equations (1978/1980) were validated on specific populations; results may vary. Skinfold accuracy depends heavily on technique and caliper quality. This tool does not replace assessment by a qualified fitness professional, dietitian, or physician.

In-article · data-ad-layout="in-article"

Frequently asked questions — Skinfold body fat

What is the Jackson-Pollock 3-site method?

It is a field test developed by Jackson and Pollock (1978/1980) that measures skinfold thickness at three specific body sites in millimetres. The sum is used in a sex- and age-specific equation to estimate body density, then body fat via the Siri equation (495/density − 450).

Which sites are measured for men and women?

For men: chest, abdomen and thigh. For women: tricep, suprailiac and thigh. The sites were chosen because they represent a reliable cross-section of subcutaneous fat distribution for each sex.

Do I need to convert the skinfold measurements to imperial?

No. Skinfold measurements are always entered in millimetres (mm), regardless of whether you have selected metric or imperial mode. Only body weight (for lean and fat mass calculation) uses the unit toggle.

How accurate is the skinfold method?

With a trained measurer and a quality caliper, the 3-site Jackson-Pollock method has a standard error of about ±3–4% body fat, making it one of the most practical and validated field assessments available.

What body fat percentage is considered healthy?

General guidelines: for men, 10–20% is considered fit to average healthy; for women, 18–28%. Athletes typically sit 5–15% (men) or 12–22% (women). These ranges vary by age and source — use them as reference, not rigid targets.

📚 Learn more — official sources

🔬 Study Jackson & Pollock (1978) — Generalized equations for predicting body density Original article establishing the 3-site skinfold equations for men. See on PubMed → 🔬 Study Jackson, Pollock & Ward (1980) — Generalized equations for women The companion article extending the 3-site equations to women. See on PubMed → 🏛️ Organization ACE — Skinfold Measurement American Council on Exercise: body fat percentage ranges and skinfold measurement guidance. See official source → 📘 Guide ACSM — Body Composition Assessment American College of Sports Medicine guidelines for body composition testing and interpretation. See official source →

Body fat — skinfolds

Did this calculator help you?

84 people found these tools useful

Suggest an improvement or a new calculator

⏱ You've already sent 3 suggestions today. Come back tomorrow to contribute again!

📧 Enter your email to confirm — we don't publish it, we only get in touch if we want to use your idea.

✅ Got it! Thank you — your idea goes onto our improvements list.

About the Body Fat Skinfold Calculator

The Jackson-Pollock 3-site method is one of the most widely validated field tests for estimating body composition. Unlike underwater weighing or DEXA scans, it requires only a skinfold caliper and a trained hand — making it practical for gyms and clinics worldwide.

This tool implements the original 1978 (men) and 1980 (women) regression equations. Skinfolds are always entered in millimetres. The unit toggle controls only body weight units — used optionally to break down lean and fat mass. All calculations are transparent and explained step by step.