Lean Body Mass & FFMI Calculator

Your Measurements

Gender

Age (years)

Height (cm)

Weight (kg)

Body Fat Percentage (%)

Don't know your body fat %? Use our Body Fat Calculator

Your Results

Lean Body Mass (Boer Formula)

0 kg

Non-fat tissue mass

Fat Mass

0 kg

Body fat weight

Fat-Free Mass Index (FFMI)

0

-

Normalized FFMI

0

Adjusted to 1.8m height

FFMI Reference Ranges

Below Average: <17 (men), <14 (women)

Average: 18-20 (men), 15-17 (women)

Above Average: 20-22 (men), 17-19 (women)

Excellent: 22-23 (men), 19-20 (women)

Superior: 23-26 (men), 20-22 (women)

Suspicion Threshold: >25 (natural limit)

💡 Interpretation

How It Works

Step 1: Calculate Lean Body Mass (Boer Formula)

Males: LBM = 0.407 × Weight(kg) + 0.267 × Height(cm) - 19.2
Females: LBM = 0.252 × Weight(kg) + 0.473 × Height(cm) - 48.3

The Boer formula estimates lean mass based on weight and height, validated through DEXA scan studies.

Step 2: Calculate Fat Mass

Fat Mass = Total Weight × (Body Fat % / 100)

Step 3: Calculate FFMI (Fat-Free Mass Index)

FFMI = LBM(kg) / [Height(m)]²
Normalized FFMI = FFMI + 6.1 × (1.8 - Height(m))

FFMI is similar to BMI but uses lean mass instead of total weight. Normalized FFMI adjusts for height to allow fair comparison between individuals.

Example Calculation

Example: Male, 30 years, 175 cm, 75 kg, 18% body fat

Step 1: LBM = 0.407×75 + 0.267×175 - 19.2 = 58.1 kg
Step 2: Fat Mass = 75 × 0.18 = 13.5 kg
Step 3: FFMI = 58.1 / 1.75² = 19.0
Result: Average to above-average muscle mass

Frequently Asked Questions

What is lean body mass? ▼

Lean body mass (LBM) is your total body weight minus fat mass. It includes muscle, bone, organs, water, and connective tissue. LBM is a better predictor of metabolic rate than total body weight.

What is a good FFMI score? ▼

For men, 18-20 is average, 20-22 is above average, and 22-23 is excellent. Values above 25 are rare without pharmaceutical assistance. For women, 15-17 is average, 17-19 is above average, and 19-20 is excellent.

How can I increase my lean body mass? ▼

Progressive resistance training (weightlifting) combined with adequate protein intake (1.6-2.2g per kg bodyweight) and a slight caloric surplus builds lean mass. Consistency over months and years is key.

Why use FFMI instead of BMI? ▼

BMI doesn't distinguish between fat and muscle. An athlete with high muscle mass may have a high BMI but low body fat. FFMI accounts for body composition, making it more accurate for assessing health and fitness.

What's the difference between Boer and other LBM formulas? ▼

The Boer formula (1984) is widely validated and commonly used in clinical settings. Other formulas like James (1976) or Hume (1966) give similar results but may differ by 1-3 kg. Boer is preferred for its accuracy across diverse populations.

References & Sources

📚

Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans

Am J Physiol. 1984 Oct;247(4 Pt 2):F632-6

📚

Kouri EM, et al. Fat-free mass index in users and nonusers of anabolic-androgenic steroids

Clin J Sport Med. 1995 Oct;5(4):223-8

📚

Lean Body Mass Calculator - Calculator.net

Comprehensive guide to LBM calculation methods and interpretation

📚

Fat-free mass - Wikipedia

Overview of fat-free mass concepts and measurement methods