Lean body mass, not just weight.
Everything that isn't fat — muscle, bone, organs, water — expressed as kg or lb.
Lean body mass
Lean body mass
58.0–59.0 kg
- Boer (1984)58.0 kg
- James (1976)59.0 kg
Fat mass
17.0kg
FFMI
19.0
Normalised: 19.3
Skeletal muscle ≈
23.2–29.0kg
40–50% of lean mass.
Good to know
What's the difference between lean mass and muscle mass?+
Lean body mass includes muscle, bone, organs, and water — everything that isn't fat. Skeletal muscle typically makes up 40–50% of lean mass.
What's FFMI?+
Fat-free mass index normalises lean mass against height, like BMI. Normalised FFMI of ~25 is a natural ceiling for men without performance-enhancing drugs; above that raises questions.
Which formula is most accurate?+
If you know your body fat %, use that directly — most accurate. Boer is generally favoured for clinical use; James is older but still cited. Provide both for context.
