Question 1

How accurate is a lean body mass calculator?

Accepted Answer

Formula-based estimates like Boyle and Hume are good ballparks for typical builds and great for tracking change over time, but they can be off for very muscular or very lean people. For a precise number, measure your body fat percentage (and subtract it from your weight) or get a DEXA scan.

Question 2

What's the difference between lean body mass and muscle mass?

Accepted Answer

Muscle is part of lean body mass, but LBM also includes bone, organs, and water. Skeletal muscle is usually around 40–50% of lean mass, so LBM is always larger than your muscle mass alone.

Question 3

How do I increase lean body mass?

Accepted Answer

Resistance training plus enough protein (roughly 1.2–2.0 g per kg of body weight for active adults) and adequate total calories. Building lean mass while in a calorie deficit is possible but slow — most people gain it fastest at maintenance or a slight surplus.

Question 4

Why does lean mass matter for weight loss?

Accepted Answer

Lean mass burns more calories at rest than fat does, so preserving it keeps your metabolism higher as you lose weight. Crash diets that ignore protein and training tend to shed lean mass along with fat, which makes weight regain easier.

Lean Body Mass Calculator — Boyle & Hume Formulas, Fat-Free Mass (2026)