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🏋️ Your Body Details
Enter your details to calculate lean body mass
💪 Your Body Composition
Lean Mass
64.0 kg
80%
Fat Mass
16.0 kg
20%
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What is Lean Body Mass?
Lean Body Mass (LBM) is the total weight of your body minus all fat mass. It includes muscle, bones, organs, skin, water and everything else that is not fat. LBM is a more meaningful health metric than total body weight because it tells you how much functional tissue your body contains.
Lean Body Mass = Total Body Weight × (1 - Body Fat Percentage)
Fat Mass = Total Body Weight × Body Fat Percentage
Example: 80 kg person with 20% body fat:
Fat Mass = 80 × 0.20 = 16 kg
Lean Body Mass = 80 - 16 = 64 kg
Boer Formula (alternative):
Men: LBM = 0.407W + 0.267H - 19.2
Women: LBM = 0.252W + 0.473H - 48.3
Where W = weight kg, H = height cm
Why Lean Body Mass Matters More Than Weight
Two people can weigh exactly the same but have completely different body compositions. A 80kg person with 15% body fat has 68kg of lean mass and looks very different from a 80kg person with 30% body fat who has only 56kg of lean mass. Tracking LBM over time tells you whether you are genuinely building muscle or just gaining weight.
How to Increase Lean Body Mass
- Progressive resistance training — lifting weights stimulates muscle protein synthesis
- Adequate protein intake — 1.6-2.2g per kg of body weight supports muscle growth
- Calorie surplus for muscle gain — a modest surplus of 200-300 calories above TDEE
- Sufficient sleep — most muscle repair happens during deep sleep
- Consistency — muscle building is a slow process measured in months not weeks
⚠️ Health Disclaimer: This lean body mass calculator provides estimates for informational and educational purposes only and is not a substitute for professional medical advice. Body composition calculations based on body fat percentage are estimates and actual values may vary. For precise body composition measurement consult a healthcare professional using methods such as DEXA scanning.
Frequently Asked Questions
What is a good lean body mass percentage? +
There is no single ideal lean body mass percentage since it depends on your total body fat. Generally a healthy body fat of 14-17% for men and 21-24% for women means lean mass of 83-86% for men and 76-79% for women. Athletes often have lean mass percentages of 85-92%. The higher your lean mass percentage the lower your body fat which is generally associated with better health outcomes.
How is lean body mass different from muscle mass? +
Lean body mass includes everything that is not fat — muscle, bones, organs, water, connective tissue and skin. Muscle mass refers specifically to skeletal muscle tissue. Skeletal muscle typically makes up about 40-50% of lean body mass in healthy adults. So if your lean body mass is 70 kg your skeletal muscle mass is approximately 28-35 kg depending on your fitness level and genetics.
How do I calculate lean body mass without knowing body fat? +
Use the Boer formula which estimates LBM from height and weight alone. For men: LBM = 0.407 × weight(kg) + 0.267 × height(cm) - 19.2. For women: LBM = 0.252 × weight(kg) + 0.473 × height(cm) - 48.3. However for greater accuracy we recommend using our Body Fat Calculator first to get your body fat percentage then entering it above for a more precise lean mass calculation.
Can lean body mass decrease while losing weight? +
Yes — when losing weight too aggressively or with insufficient protein intake your body can break down muscle tissue for energy. This is called muscle wasting or catabolism. To minimize lean mass loss during weight loss eat adequate protein (1.6-2.0g per kg of target body weight), perform resistance training and aim for a moderate calorie deficit of 300-500 calories per day rather than extreme restriction.
Why is lean body mass important for metabolism? +
Muscle tissue is metabolically active — it burns calories even at rest. For every kilogram of muscle you have your body burns approximately 13 calories per day just to maintain it. Fat tissue burns only about 4 calories per kg per day. This is why people with higher lean body mass have higher resting metabolic rates and can eat more without gaining fat. Building muscle is one of the most effective long term strategies for maintaining a healthy weight.