Lean Body Mass Calculator
Estimate your lean body mass — your fat-free weight — using the Boer formula. A key number for protein targets and muscle tracking.
Lean body mass
57.1 kg
82% of your body weight is lean tissue.
Lean mass
57.1
Est. fat mass
12.9
Understanding lean body mass
Lean body mass is the total weight of everything in your body except stored fat: your muscles, bones, organs, blood, and water. It's the engine of your metabolism, since lean tissue burns considerably more energy at rest than fat does.
Why it's worth tracking
When you lose weight, the goal is to lose fat while keeping lean mass. Tracking LBM alongside your body fat percentage confirms you're doing exactly that. If your lean mass is dropping, you likely need more protein or a smaller deficit.
From LBM to protein needs
Many coaches set protein targets relative to lean body mass rather than total weight, which is especially useful for those with higher body fat. Check the protein calculator to translate your numbers into a daily gram target.
Frequently asked questions
What is lean body mass?
Lean body mass (LBM) is everything in your body that isn't fat — muscle, bone, organs, water, and connective tissue. It's a key reference point for setting protein needs and tracking muscle during weight changes.
How is lean body mass calculated?
This calculator uses the Boer formula, which estimates LBM from your sex, height, and weight. It's one of the most widely used equations and works well for the general population.
Why does lean body mass matter?
LBM drives your metabolism — more lean mass means a higher resting calorie burn. Preserving it during weight loss keeps your metabolism strong and your body looking toned rather than 'skinny fat'.
How can I increase lean body mass?
Resistance training combined with adequate protein (1.6–2.2 g/kg) and a slight calorie surplus is the proven recipe for building lean mass over time.