What is the Siri equation?

The Siri equation (1956) converts body density to body fat percentage: %BF = (4.95/BD - 4.50) x 100, where BD is body density in g/mL. It assumes fat density of 0.9 g/mL.

When is the 7-site skinfold used?

The 7-site protocol (chest, midaxillary, tricep, subscapular, abdomen, suprailiac, thigh) provides greater accuracy than 3-site methods and is preferred for research and elite sports assessment.

Are there limitations to the Siri equation?

The Siri equation assumes constant fat-free mass density, which varies with age, sex, ethnicity, and hydration. Alternative formulas by Brozek or Schutte may be more appropriate for some populations.

Siri Equation Body Fat from Body Density

Calculate body fat percentage from body density: %BF = (4.95/BD - 4.50) x 100. Used after 7-site skinfold sum.

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Frequently Asked Questions

What is the Siri equation?

When is the 7-site skinfold used?

Are there limitations to the Siri equation?