Lean Body Mass Calculator
LBM Formulas
Boer Formula
Male: 0.407W + 0.267H - 19.2
Female: 0.252W + 0.473H - 48.3
James Formula
Male: 1.1W - 128(W/H)^2
Female: 1.07W - 148(W/H)^2
Hume Formula
Male: 0.328W + 0.339H - 29.5
Female: 0.296W + 0.418H - 43.3
W = Weight (kg), H = Height (cm)
Typical LBM Values
Understanding Lean Body Mass
Lean Body Mass (LBM), also known as Fat-Free Mass (FFM), is the total weight of your body minus all the weight due to fat mass. It includes muscle, bone, organs, skin, and body water. LBM is an important metric for fitness enthusiasts and medical professionals.
What Makes Up Lean Body Mass?
- Skeletal muscle: The largest component (~40% of body weight in men)
- Bones: Approximately 15% of total body weight
- Organs: Heart, liver, kidneys, brain, etc.
- Blood and body water: About 60% of body weight is water
- Connective tissue: Tendons, ligaments, cartilage
- Skin: The body's largest organ
Why LBM Matters
For Fitness
- Track muscle gain during bulking
- Monitor fat loss vs. muscle loss
- Set realistic body composition goals
- Calculate protein needs
For Medicine
- Drug dosing calculations
- Nutrition assessment
- Metabolic rate estimation
- Kidney function assessment
LBM vs. Body Fat Percentage
The relationship is simple: Total Body Weight = Lean Body Mass + Fat Mass
If you weigh 180 lbs with 20% body fat:
- Fat Mass = 180 × 0.20 = 36 lbs
- Lean Body Mass = 180 - 36 = 144 lbs (80% of body weight)
Increasing Lean Body Mass
- Resistance training: The most effective way to build muscle
- Adequate protein: 0.7-1g per pound of body weight
- Caloric surplus: Needed for muscle growth (or at least maintenance for recomp)
- Rest and recovery: Muscles grow during rest
- Progressive overload: Gradually increase weight/volume
Important Note
These formulas provide estimates based on statistical averages. Individual variations in body composition, muscle mass, and bone density mean actual LBM may differ from calculated values. For precise measurements, consider DEXA scans, hydrostatic weighing, or BodPod testing.
Frequently Asked Questions
What is lean body mass (LBM)?
Lean body mass is your total body weight minus fat mass. It includes muscle, bones, organs, skin, blood, and water - everything except stored fat. For men, LBM is typically 75-85% of total body weight; for women, 70-80%. Athletes and very lean individuals may have LBM percentages above 85% (men) or 80% (women).
Why is knowing my lean body mass important?
LBM is useful for tracking fitness progress (are you gaining muscle or just weight?), calculating accurate protein needs (based on lean mass rather than total weight), medical purposes like drug dosing, and setting realistic body composition goals. It provides better insight than scale weight alone.
How can I increase my lean body mass?
To increase LBM, focus on resistance training with progressive overload, consume adequate protein (1.6-2.2g per kg body weight), eat at a slight caloric surplus for muscle growth, prioritize sleep and recovery, and be patient - natural muscle gain is about 0.5-1 pound per month for trained individuals.
How accurate are lean body mass formulas?
LBM formulas like Boer, James, and Hume provide estimates based on statistical averages. They're reasonably accurate for most people but may be off for very muscular or obese individuals. For precise measurements, consider DEXA scans, hydrostatic weighing, or BodPod testing. Formula estimates are best for tracking changes over time.