📐 4-Site Skinfold Calculator
Calculate your body fat percentage using the classic Durnin & Womersley (1974) 4-site skinfold method
4-Site Skinfold Calculator: Complete Durnin & Womersley Guide
The Durnin & Womersley (1974) 4-site skinfold method is the classic gold standard for body fat assessment using calipers. This scientifically validated protocol provides accurate body composition analysis using four measurement sites: biceps, triceps, subscapular, and suprailiac. Measurements can be taken in millimeters (mm) or inches with automatic conversion for precise calculations.
📏 Classic 4-Site Protocol
The Durnin & Womersley method uses four specific skinfold sites for both men and women. Research demonstrates this approach with high correlation coefficients compared to hydrostatic weighing across diverse populations.
🔬 Age-Specific Equations
Uses age-specific logarithmic equations for different age groups (16-19, 20-29, 30-39, 40-49, 50+ years). Studies validate the age-specific approach for improved accuracy across the lifespan.
⚖️ Universal Sites
All Participants: Biceps, Triceps, Subscapular, Suprailiac
Unlike other methods, Durnin & Womersley uses the same four sites for both genders, making it simpler to administer.
📊 Body Fat Standards by Age and Gender
| Category | Men (18-29) | Men (30-49) | Men (50+) | Women (18-29) | Women (30-49) | Women (50+) |
|---|---|---|---|---|---|---|
| Essential Fat | 2-5% | 2-5% | 2-5% | 10-13% | 10-13% | 10-13% |
| Athletes | 6-13% | 7-16% | 9-18% | 14-20% | 16-23% | 18-27% |
| Fitness | 14-17% | 17-19% | 19-21% | 21-24% | 24-27% | 27-30% |
| Average | 18-24% | 21-27% | 24-29% | 25-31% | 28-34% | 31-37% |
| Above Average | 25%+ | 28%+ | 30%+ | 32%+ | 35%+ | 38%+ |
📐 4-Site Measurement Instructions
💪 Biceps Skinfold
Location: Vertical fold on the front of the upper arm
Technique: Measure over the belly of the biceps muscle, midway between the acromion and olecranon processes
Direction: Fold runs parallel to the long axis of the arm
🔧 Triceps Skinfold
Location: Vertical fold on the back of the upper arm
Technique: Measure over the triceps muscle, midway between acromion and olecranon
Direction: Fold runs parallel to the long axis of the arm
🎯 Subscapular Skinfold
Location: Diagonal fold below the inferior angle of the scapula
Technique: Fold follows the natural line of the skin, approximately 45° to horizontal
Direction: Diagonal fold running medially downward
⚡ Suprailiac Skinfold
Location: Diagonal fold above the iliac crest
Technique: Measure at the anterior axillary line, above the iliac crest
Direction: Fold follows the natural line of the skin
🧮 Durnin & Womersley Formula & Protocol
Step 1: Take Measurements
• Use calibrated skinfold calipers (Lange, Harpenden, or similar)
• Take 3 measurements at each site, use median value
• Apply 10g/mm² pressure consistently
• Read measurement 2 seconds after full pressure applied
Step 2: Calculate Body Density (Age-Specific Equations)
Men (Durnin & Womersley, 1974):
16-19 years: BD = 1.1620 - (0.0630 × log₁₀(Sum))
20-29 years: BD = 1.1631 - (0.0632 × log₁₀(Sum))
30-39 years: BD = 1.1422 - (0.0544 × log₁₀(Sum))
40-49 years: BD = 1.1620 - (0.0700 × log₁₀(Sum))
50+ years: BD = 1.1715 - (0.0779 × log₁₀(Sum))
Women (Durnin & Womersley, 1974):
16-19 years: BD = 1.1549 - (0.0678 × log₁₀(Sum))
20-29 years: BD = 1.1599 - (0.0717 × log₁₀(Sum))
30-39 years: BD = 1.1423 - (0.0632 × log₁₀(Sum))
40-49 years: BD = 1.1333 - (0.0612 × log₁₀(Sum))
50+ years: BD = 1.1339 - (0.0645 × log₁₀(Sum))
Step 3: Convert to Body Fat %
Body Fat % = ((4.95 ÷ Body Density) - 4.50) × 100
Using the Siri equation (1961)
Example: 25-year-old male, measurements: Biceps 6mm, Triceps 10mm, Subscapular 12mm, Suprailiac 8mm
Sum = 36mm, log₁₀(36) = 1.556, BD = 1.0647, Body Fat = 15.9%
Result: Fitness category for age group
💡 Measurement Tips & Best Practices
Proper Technique
Pinch skin and fat away from muscle. Maintain 10g/mm² pressure. Take measurements on right side of body. Ensure consistent technique across all four sites.
Timing Considerations
Measure at same time of day. Avoid post-exercise or post-meal measurements. Ensure proper hydration status for consistency.
Reliability
Take 3 measurements per site, use median value. Repeat measurements if values differ by >2mm. Train for consistency across sessions.
Equipment Quality
Use calibrated calipers (±0.5mm accuracy). Popular brands: Lange, Harpenden, Accu-Measure. Regular calibration ensures measurement accuracy.
⚖️ Method Comparison & Historical Significance
The Durnin & Womersley (1974) method is considered the foundational work in skinfold body composition assessment. Historical analysis shows its lasting impact:
| Method | Year | Sites | Age Groups | Sample Size | Correlation (r) |
|---|---|---|---|---|---|
| Durnin & Womersley | 1974 | 4 sites | 5 groups | 481 subjects | 0.92-0.97 |
| Jackson & Pollock (Men) | 1978 | 3 sites | Continuous | 403 subjects | 0.91 |
| Jackson, Pollock & Ward (Women) | 1980 | 3 sites | Continuous | 249 subjects | 0.84 |
| Slaughter et al. | 1988 | 2 sites | Youth only | 310 subjects | 0.89 |
Historical Significance:
- First comprehensive age-specific skinfold equations
- Established the 4-site measurement protocol
- Validated across wide age range (16-72 years)
- Used logarithmic transformation for improved accuracy
- Foundation for subsequent skinfold research
- Still widely used in clinical and research settings
🏥 Clinical Applications & Research Uses
Clinical Assessment
Applications: Obesity evaluation, weight loss monitoring, metabolic health assessment
Advantages: Non-invasive, cost-effective, no radiation exposure, suitable for repeated measurements
Research Applications
Uses: Population studies, intervention trials, epidemiological research, athletic performance studies
Benefits: Standardized protocol, age-specific equations, extensive validation literature
Population Studies
Scope: Large-scale health surveys, cross-cultural studies, longitudinal aging research
Value: Validated across diverse populations and ethnic groups
Limitations & Considerations
Factors: Requires trained technician, affected by hydration, assumes constant tissue density
Accuracy: ±3-4% standard error when performed correctly by experienced practitioners
🔬 Modern Applications & Updates
While the original Durnin & Womersley equations remain valid, modern applications have expanded their use:
- Digital Calipers: Modern digital calipers provide more precise measurements and data logging
- Population-Specific Equations: Ethnicity-specific modifications for improved accuracy in diverse populations
- Athletic Populations: Specialized applications for very lean athletes and bodybuilders
- Pediatric Applications: Modified protocols for children and adolescents
- Geriatric Studies: Age-related considerations for older adults (>70 years)
- Technology Integration: Apps and software for automated calculations and progress tracking
Quality Assurance Guidelines:
- Technician training and certification programs
- Inter-rater reliability testing (>0.95 correlation)
- Caliper calibration with standard blocks
- Standardized measurement protocols and timing
- Documentation of measurement conditions and subject preparation
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References
- Davidson LE, Wang J, Thornton JC, Kaleem Z, Silva-Palacios F, Pierson RN, Heymsfield SB, Gallagher D. Predicting fat percent by skinfolds in racial groups: Durnin and Womersley revisited. Med Sci Sports Exerc. 2011 Mar;43(3):542-9. doi: 10.1249/MSS.0b013e3181ef3f07. PMID: 20689462; PMCID: PMC3308342.
- Peterson, M. J., Czerwinski, S. A., & Siervogel, R. M. (2003). Development and validation of skinfold-thickness prediction equations with a 4-compartment model. The American Journal of Clinical Nutrition, 77(5), 1186-1191. https://doi.org/10.1093/ajcn/77.5.1186
- Chambers AJ, Parise E, McCrory JL, Cham R. A comparison of prediction equations for the estimation of body fat percentage in non-obese and obese older Caucasian adults in the United States. J Nutr Health Aging. 2014;18(6):586-90. doi: 10.1007/s12603-014-0017-3. PMID: 24950148; PMCID: PMC4396823.
