Skinfold Body Fat Calculator
Estimate body-fat percentage with the Jackson–Pollock 3-site or 7-site method.
See your estimate
Your body-fat estimate, fat mass, lean body mass, and skinfold total will appear here.
Estimated body fat
This scenario assumes lean body mass remains unchanged.
Calculation details
Body fat = (495 ÷ body density) − 450
Estimate only. Measurement technique and equation assumptions can affect the result. Accuracy and limitations
What Is a Skinfold Body-Fat Calculator?
Skinfold calipers measure folds of skin and subcutaneous fat. The Jackson–Pollock equation converts selected measurements into estimated body density, and the Siri equation converts density into estimated body-fat percentage.
Three-Site Versus Seven-Site Testing
The 3-site method is faster and easier to perform. The 7-site method collects more detail, but it is not automatically more accurate for every person; consistent site location and measurement technique can matter more than taking additional sites.
Which Measurements Does Each Method Use?
| Method | Male-equation sites | Female-equation sites | Best use |
|---|---|---|---|
| 3-site | Chest, abdomen, thigh | Triceps, suprailiac, thigh | Faster and easier testing |
| 7-site | Chest, midaxillary, triceps, subscapular, abdomen, suprailiac, thigh | Same seven sites | More detailed measurement protocol |
See the measurement guide before taking readings.
How the Calculation Works
The calculator sums the required measurements, applies the selected age-adjusted Jackson–Pollock body-density equation, then uses the Siri conversion: body fat % = (495 ÷ density) − 450. Full precision is retained until results are displayed.
How to Interpret the Estimate
Treat the number as an estimate and focus on trends collected under consistent conditions. It is not a diagnosis and does not prescribe a body-fat target.
Fat Mass Versus Lean Body Mass
Fat mass is body weight multiplied by the estimated fat fraction. Lean body mass is everything else—including water, bone, organs, muscle, and other non-fat tissue—so it is not equivalent to muscle mass.
Goal-Weight Calculation and Its Assumption
Optional goal weight equals estimated lean body mass divided by one minus the target fat fraction. This scenario holds lean body mass constant; real changes may also involve water, glycogen, muscle, bone, and other tissue.
Accuracy and Limitations
Technique, site placement, calipers, hydration, tissue compressibility, and fit with the source equations can affect the estimate. Results can differ from DEXA, hydrostatic weighing, bioelectrical impedance, and other methods.
Frequently Asked Questions
Are measurements entered in inches?
No. Every skinfold must be entered in millimeters.
Does the calculator measure visceral fat?
No. Skinfolds assess subcutaneous folds and do not directly measure visceral fat.
Should I choose the 7-site method?
Choose it when you can locate and measure all seven sites consistently. More sites do not guarantee a better individual estimate.
Sources
- Jackson AS, Pollock ML. Generalized equations for predicting body density of men. British Journal of Nutrition. 1978.
- Jackson AS, Pollock ML, Ward A. Generalized equations for predicting body density of women. Medicine & Science in Sports & Exercise. 1980.
- Siri WE. Body Composition from Fluid Spaces and Density: Analysis of Methods. In: Techniques for Measuring Body Composition. 1961.