Enter your weight and body fat percentage to split your bodyweight into fat and everything else.
Estimates are for general guidance only and are not medical advice. For a personalised plan, book a free guided tour at RPM Gym.
Lean body mass is everything you weigh that isn't fat: muscle, bone, organs, connective tissue and the water in all of it. It is not a muscle-mass measurement, and the difference matters. Roughly half your lean mass is skeletal muscle; the rest is structure and fluid you can't train.
The number's real use is as a denominator. Protein needs for lean, resistance-trained people in a deficit are expressed per kilogram of fat-free mass rather than bodyweight, and drug and anaesthetic dosing works the same way. Anywhere a figure needs to ignore fat tissue, this is the figure it uses.
Its second use is directional. In a deficit, weight falling while lean mass holds is the outcome you want, and weight falling with lean mass is the one that means the deficit is too steep or protein and training are too light. One weigh-in tells you nothing about that. Two months of them tells you a lot.
Fat mass = weight × (body fat % ÷ 100) Lean body mass = weight − fat mass
An 85 kg man who has estimated his body fat at 20%.
68 kg of lean mass. If a three-point measurement error puts his true body fat at 17% or 23%, his lean mass is 70.6 kg or 65.5 kg instead — a 5 kg swing from a rounding error, which is why the trend matters more than the reading.
Everything you weigh minus your fat: muscle, bone, organs, connective tissue and body water. It's sometimes called fat-free mass, and the two terms are used interchangeably in most training contexts.
No, and confusing them overstates how much muscle you carry. Skeletal muscle is roughly half of lean body mass in an adult; the rest is bone, organs and fluid. A calculator that reports 68 kg of lean mass is not reporting 68 kg of muscle.
There isn't a published band, because the figure scales with height and skeletal frame. A 165 cm and a 190 cm adult at the same body fat percentage will have very different lean masses and both can be perfectly healthy. Direction over time is the meaningful reading, not the absolute number.
Progressive resistance training, enough protein, and enough total calories — a surplus if you want it to happen at any speed. Recomposition at maintenance is possible, particularly for beginners and people returning after a break, but it's slower.
Most often water and glycogen rather than tissue. Cutting carbohydrate sharply drops stored glycogen and the water bound to it, and both sit inside the lean compartment. Look at a four-to-six week trend before drawing any conclusion.
Programming and protein are what protect lean mass through a cut. Talk both through on a free guided tour at RPM Gym in Al Manhal.