Calculator Form
Formula Used
Male body density: BD = 1.10938 - 0.0008267S + 0.0000016S² - 0.0002574A
Female body density: BD = 1.0994921 - 0.0009929S + 0.0000023S² - 0.0001392A
Siri conversion: Body Fat % = 495 / BD - 450
Brozek conversion: Body Fat % = 457 / BD - 414.2
Variables: S is the sum of three skinfolds in millimeters. A is age in years. BD is body density.
How To Use This Calculator
- Select sex, because each equation uses different skinfold sites.
- Enter age in completed years.
- Measure each skinfold site in millimeters.
- Enter body weight if you want fat mass and lean mass.
- Choose Siri or Brozek conversion.
- Press Calculate to view the result above the form.
- Use CSV or PDF buttons to save the calculation.
Example Data Table
| Sex | Age | Site 1 | Site 2 | Site 3 | Sum | Estimated Body Fat |
|---|---|---|---|---|---|---|
| Male | 30 | 12 mm Chest | 20 mm Abdomen | 15 mm Thigh | 47 mm | 15.60% |
| Female | 28 | 18 mm Triceps | 16 mm Suprailiac | 24 mm Thigh | 58 mm | 24.28% |
| Male | 42 | 18 mm Chest | 28 mm Abdomen | 20 mm Thigh | 66 mm | 22.07% |
Three Site Skinfold Guide
The three site skinfold method estimates body fat from caliper readings. It is popular because it is quick, portable, and repeatable. This calculator uses the Jackson Pollock three site equations. It then converts body density into body fat percentage with the selected conversion formula.
Why Skinfold Testing Helps
Skinfold testing measures subcutaneous fat at chosen body locations. Men usually use chest, abdomen, and thigh sites. Women usually use triceps, suprailiac, and thigh sites. These sites represent common fat storage patterns. A trained tester can repeat the same landmarks and reduce error.
Good data matters. Pinch the fold firmly. Place the caliper jaws about one centimeter below the fingers. Read after one or two seconds. Take each site at least twice. If readings differ widely, test again and use the average.
What The Result Means
The calculator first adds the three skinfold values. Age and sex are then applied to the density equation. Higher skinfold totals usually reduce body density. Lower density usually means a higher fat percentage. The tool also estimates fat mass and lean mass when body weight is entered.
You can compare the Siri and Brozek conversions. Siri is common in fitness reports. Brozek is also used in body composition research. Differences are usually small, but the comparison can help with record keeping.
Practical Use
Use the same caliper, side of body, and time of day. Avoid testing right after training, bathing, or heavy sweating. Hydration, tester skill, and site placement can change results. Treat one test as an estimate. Treat repeated tests as a trend.
This page also includes target body fat planning. Enter a target percentage to estimate the body weight that would match current lean mass. This assumes lean mass stays stable, so it is only a planning guide. For medical decisions, use a qualified professional. For fitness tracking, combine this tool with photos, waist measures, strength data, and consistent notes.
Important Limits
The equation was built from population samples. It may be less accurate for very lean athletes, older adults, and people with unusual fat distribution. Still, it is useful when technique stays consistent. Track averages across weeks. Do not judge progress from one reading alone. Use careful testing habits.
FAQs
What is a 3 site skinfold calculator?
It estimates body fat using three caliper readings, age, and sex. The result is based on body density equations and a body fat conversion formula.
Which sites are used for men?
The common Jackson Pollock three site method for men uses chest, abdomen, and thigh measurements. Each reading should be taken in millimeters.
Which sites are used for women?
The common Jackson Pollock three site method for women uses triceps, suprailiac, and thigh measurements. Use the same landmarks during each test.
Is the result exact?
No. It is an estimate. Caliper skill, hydration, site placement, and equation limits can affect the final number.
Should I use Siri or Brozek?
Siri is common in many fitness settings. Brozek is another recognized conversion. Use the same choice for consistent progress tracking.
Why enter body weight?
Body weight lets the calculator estimate fat mass and lean mass. Without weight, it can still estimate body density and body fat percentage.
How often should I test?
Testing every two to four weeks is usually enough. Frequent tests may show normal measurement noise instead of real body composition change.
Can this replace medical testing?
No. It is a practical tracking tool. For health risks, clinical assessment, or treatment decisions, consult a qualified professional.