Lean Body Mass Calculator
Calculate your lean body mass (LBM) — the weight of your muscles, bones, and organs. Use your LBM to get the most accurate TDEE estimate with the Katch-McArdle formula.
Most accurate. Requires knowing your body fat percentage.
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The lean body mass calculator gives you two ways to estimate your LBM. Method A uses your known body fat percentage for a direct, accurate calculation. Method B uses the Boer formula (1984) — a validated estimation method that only requires your body weight, height, and sex when body fat percentage is unknown.
What Is Lean Body Mass?
Lean body mass (LBM) is the total weight of your body excluding all fat tissue. It includes:
- Skeletal muscle — the largest component, typically 40–50% of LBM
- Bone mass — approximately 15% of LBM
- Organ mass — heart, lungs, liver, kidneys, and other organs
- Body water — blood, intracellular fluid, and extracellular fluid
- Connective tissue — tendons, ligaments, cartilage
How to Use This Calculator
Method A (most accurate): Enter your total body weight and your body fat percentage. The calculator will directly compute LBM = weight × (1 − body fat%). Use the Body Fat Calculator to find your body fat percentage first.
Method B (estimation): Enter your body weight, height, and sex. The calculator uses the Boer formula to estimate LBM. This is less accurate than Method A but useful when body fat percentage is unknown.
How We Calculate Lean Body Mass
Method A: Direct Calculation
LBM = Total Weight × (1 − Body Fat% / 100)
This is mathematically exact given accurate inputs. The accuracy depends entirely on the accuracy of the body fat percentage used.
Method B: Boer Formula (1984)
Male: LBM (kg) = (0.407 × weight_kg) + (0.267 × height_cm) − 19.2
Female: LBM (kg) = (0.252 × weight_kg) + (0.473 × height_cm) − 48.3
The Boer formula is the most accurate of the LBM estimation formulas without body fat percentage, validated against hydrostatic weighing across a large population sample.
The Katch-McArdle BMR Formula
Once your LBM is known, the Katch-McArdle formula provides the most accurate BMR estimate:
BMR = 370 + (21.6 × LBM in kg)
This formula is particularly valuable for athletes and highly muscular individuals, where standard BMR formulas (Mifflin-St Jeor, Harris-Benedict) that use total body weight tend to underestimate calorie needs — because they effectively "count" metabolically inactive fat tissue as if it were consuming calories at the same rate as muscle.
LBM Reference Ranges by Height
| Height | Average Male LBM | Athletic Male LBM | Average Female LBM | Athletic Female LBM |
|---|---|---|---|---|
| 5'4" / 163cm | 52–60 kg | 65–75 kg | 38–46 kg | 48–56 kg |
| 5'7" / 170cm | 56–65 kg | 70–80 kg | 42–50 kg | 52–60 kg |
| 5'10" / 178cm | 62–72 kg | 76–86 kg | 45–54 kg | 56–64 kg |
| 6'0" / 183cm | 66–76 kg | 80–90 kg | 48–57 kg | 59–68 kg |
| 6'2" / 188cm | 70–80 kg | 84–94 kg | 51–60 kg | 62–72 kg |
Frequently Asked Questions
Lean body mass (LBM) is the total weight of your body minus all fat tissue. It includes muscle, bone, organs, blood, water, and connective tissue — everything that is not fat. For example, if you weigh 80 kg with 20% body fat, your lean body mass is 64 kg (80 × 0.80). LBM is a more accurate basis for calculating calorie needs, protein targets, and BMR than total body weight.
Lean body mass and muscle mass are not the same thing. Lean body mass includes all non-fat components: skeletal muscle, smooth muscle, organs, bone, blood, and body water. Skeletal muscle mass is typically 40–50% of lean body mass for most adults. When people talk about "gaining lean mass," they usually mean gaining skeletal muscle — but any increase in LBM is beneficial.
Resistance training is the most effective way to increase lean body mass — specifically skeletal muscle mass. Progressive overload (gradually increasing weight, reps, or difficulty over time) is the key training principle. Adequate protein intake (1.6–2.2g per kg of body weight, or 0.7–1g per lb) is required to support muscle synthesis. A slight calorie surplus (200–300 kcal above TDEE) accelerates muscle gain, though muscle can be gained in a maintenance or modest deficit if training hard.
Fat tissue is largely metabolically inactive — it burns very few calories at rest. Lean tissue, especially muscle, is metabolically active. The Katch-McArdle BMR formula uses lean body mass directly (BMR = 370 + 21.6 × LBM in kg), making it the most accurate BMR formula for people with above-average or below-average muscle mass. Using standard formulas like Mifflin-St Jeor with total body weight can significantly under- or over-estimate calorie needs for muscular or very overweight individuals.
Lean body mass targets vary by height, sex, and fitness goals. A useful reference: an "average" athletic male at 5'10" (178cm) might have 65–75 kg of LBM. A competitive natural bodybuilder of the same height might have 80–85 kg. For women at 5'5" (165cm), average athletic LBM is approximately 45–55 kg. These are rough guides — LBM is best tracked as a personal trend over time, not compared to absolute targets.
Method B (without body fat %) uses the Boer formula (1984), which estimates LBM from body weight, height, and sex. Compared to DEXA scans (the gold standard), the Boer formula is accurate to within ±3–5 kg for most people in a healthy weight range. Accuracy decreases significantly at very high or very low body fat percentages. For the best accuracy, use Method A with a known body fat percentage.