What is Lean Body Mass (LBM)?

Lean Body Mass equals Total Body Weight minus Body Fat Mass, representing muscle, bone, water, and organ weight.

Fitness & Health100% Client-Side · Instant Math

Body Fat Calculator

Estimate body fat percentage using the US Navy circumference method + BMI.

Units

Age

Height

Weight

lbs

Neck

Waist

Result Summary

US Navy Body Fat %

17.5%

ACE Fitness Tier: Fitness

BMI-Based Estimate %

20.3%

Body Fat Mass

30.1 lbs

Lean Body Mass

141.9 lbs

Lean Body Mass:141.9 lbs (82.5%)

Body Fat Mass:30.1 lbs (17.5%)

Health & Wellness Reference Notice

Calculations use established statistical formulas for general informational wellness guidance only and do not replace clinical diagnosis or personalized medical care.

How to Use This Calculator

Calculate body fat percentage, fat mass, lean body mass, and ACE fitness category using neck, waist, and (for women) hip measurements alongside height and weight.

1Select gender and preferred measurement system (Metric cm/kg or Imperial in/lbs).
2Enter height, weight, neck circumference, waist circumference (and hip circumference for women).
3Inspect US Navy body fat %, BMI-derived estimate, fat mass vs. lean muscle mass, and ACE fitness tier.

Standard Formula & Methodology

US Navy Male: 86.010·log10(waist - neck) - 70.041·log10(height) + 36.76 (inches)

Helpful Context & Precision Notes

Measure waist horizontally at navel level (men) or narrowest point (women) while relaxed for reproducible tracking.

All inputs stay locally inside your browser tab — nothing is uploaded or logged.

Frequently Asked Questions

When tape measurements are taken consistently, the US Navy circumference method typically correlates within 3–4% of hydrostatic weighing for general fitness tracking.