Lean Body Mass Calculator - Free LBM Estimate
Calculate your lean body mass (muscle, bone, and organs) using proven formulas or your body fat percentage. Get instant AI-powered analysis from a photo for more accurate results.
The Problem with LBM Formulas
Formula-based LBM estimates have a significant margin of error. Research published in PubMed shows that height-weight formulas can be off by ±5-10% compared to DEXA scans because they can't account for actual muscle mass versus fat distribution.
Boer/James/Hume
±5-10%- No equipment needed
- Quick calculation
- Multiple formulas
- Doesn't account for muscle
- Age and fitness not considered
- Wide margin of error
Body Fat Method
±2-3%- More accurate than formulas
- Accounts for actual composition
- Requires body fat data
- Only as accurate as BF% input
- Need separate measurement
DEXA Scan
±1-2%- Gold standard
- Detailed breakdown
- $75-150 per scan
- Requires appointment
- Radiation exposure
AI Photo Analysis
±2-3%- Fast results
- Track over time
- No equipment
- Requires photo
- Needs consistent conditions
LBM Calculator
Calculate Your LBM
Estimates LBM using height and weight. Less accurate but requires no body fat data.
Get Accurate Body Fat Data
For the most precise LBM calculation
For the most accurate LBM calculation, you need your real body fat percentage. PhysiqueAI analyzes your photo in 10 seconds to give you precise body composition data—no tape measure or calipers needed.
- Accurate body fat % for LBM calculation
- Track lean mass changes over time
- Compare your LBM to your potential
- See if you're gaining muscle or fat
- Works with mirror selfies
No credit card required
What the Research Says
LBM Formula Accuracy
A study published in PubMed comparing LBM prediction equations found that formula-based estimates have limitations:
- Boer formula most accurate for general populations
- All formulas underestimate LBM in muscular individuals
- Body fat method significantly more accurate when BF% is known
Why LBM Matters
Research from the Journal of Clinical Medicine shows that lean body mass is a better predictor of health outcomes than total weight:
- LBM correlates with metabolic rate and calorie needs
- Protein needs should be based on LBM, not total weight
- Tracking LBM shows real progress beyond scale weight
LBM Reference Ranges
LBM Percentage (Men)
Competition bodybuilders, 5-10% body fat
Regular training, visible muscle definition
Active lifestyle, healthy body composition
Typical adult male, 20-25% body fat
Higher body fat, potential health risks
LBM Percentage (Women)
Competition level, 10-15% body fat
Regular training, toned physique
Active lifestyle, healthy range
Typical adult female, 25-31% body fat
Higher body fat percentage
Why Lean Body Mass Matters
Accurate Calorie Needs
Your basal metabolic rate (BMR) is directly tied to lean mass, not total weight. Two people at 180 lbs will have vastly different calorie needs if one has 140 lbs of LBM and the other has 160 lbs. Knowing your LBM lets you calculate your true calorie needs.
Protein Requirements
Research suggests protein intake should be based on lean mass, not total weight. The common recommendation of 1.6-2.2g per kg of bodyweight becomes more precise as 2-3g per kg of lean body mass—ensuring you're eating enough to build muscle.
Track Real Progress
The scale doesn't tell the whole story. If your weight stays the same but LBM increases, you're successfully doing body recomposition—gaining muscle while losing fat. That's progress the scale can't show.
Set Realistic Goals
Knowing your current LBM helps set realistic physique goals. Natural lifters can gain about 20-25 lbs of muscle over their lifting career. Understanding where you are helps plan where you can go.
Understanding the Formulas
Boer Formula (1984)
Developed by P. Boer, this formula is considered one of the most accurate for general populations.
James Formula (1976)
W.P.T. James developed this formula, which accounts for the relationship between weight and height squared.
Hume Formula (1966)
One of the earliest LBM formulas, developed by R. Hume using regression analysis on body composition data.
Get precise body composition data
Stop guessing with formulas. Get your actual body fat percentage in 10 seconds and know your real lean body mass. Track changes over time to see if you're gaining muscle.
No credit card required • 3 free scans/month