Body Fat Calculator Formula

Understand the math behind the body fat calculator. Each variable explained with a worked example.

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Formulas Used

Body Fat Percentage

body_fat_pct = 86.010 * log10(waist - neck) - 70.041 * log10(height_inches_total) + 36.76

Lean Mass Percentage

lean_mass_pct = 100 - (86.010 * log10(waist - neck) - 70.041 * log10(height_inches_total) + 36.76)

Variables

VariableDescriptionDefault
waistWaist Circumference(inches)34
neckNeck Circumference(inches)15
height_inches_totalHeight(inches)70

How It Works

U.S. Navy Body Fat Formula (Male)

Body Fat % = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76

All measurements are in inches.

Body Fat Categories (Male)

| Category | Body Fat % | |---|---| | Essential Fat | 2-5% | | Athletes | 6-13% | | Fitness | 14-17% | | Average | 18-24% | | Obese | 25%+ |

Worked Example

A male with a 34-inch waist, 15-inch neck, and 70 inches tall.

waist = 34neck = 15height_inches_total = 70
  1. 01Waist - Neck = 34 - 15 = 19 inches
  2. 02log10(19) = 1.2788
  3. 03log10(70) = 1.8451
  4. 04Body Fat = 86.010 x 1.2788 - 70.041 x 1.8451 + 36.76
  5. 05= 110.0 - 129.2 + 36.76 = 17.5%

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