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Muscle Mass Estimate Calculator

Work out muscle mass estimate instantly with clear inputs, formula shown and shareable results.

About Muscle Mass Estimate Calculator

Lean body mass is everything that is not fat - muscle, bone, organs and water. Skeletal muscle is roughly 53% of that in adults, so an 80 kg person at 18% fat carries 65.6 kg lean and about 34.8 kg of skeletal muscle, 43% of body weight. The remainder is bone, organs and non-muscle water.

Formulas

Lean body mass

LBM = weight x (1 - body fat / 100)

Skeletal muscle

SMM is about 0.53 x LBM in adults

Worked example

With the default values below, Muscle Mass Estimate Calculator returns Estimated Skeletal Muscle Mass of 34.77. Change any input above and every figure here is recalculated in your browser.

Inputs used

Body weightminimum 1 kg
80 kg
Body fat percentageaccepts 0–70 %
18 %
Heightminimum 100 cm
178 cm

Results

Estimated Skeletal Muscle Mass
34.77 kg
Lean Body Mass
65.60 kg
Muscle As A Share Of Body Weight
43.5%
Skeletal Muscle Index
10.97 kg/m2

Step by step

  1. 1Values used
  2. 2Lean body mass
  3. 3Skeletal muscle
  4. 4Estimated Skeletal Muscle Mass= 34.77 kg
  5. 5Lean Body Mass= 65.60 kg
  6. 6Muscle As A Share Of Body Weight= 43.5
  7. 7Skeletal Muscle Index= 10.97 kg/m2

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • These figures are population-average estimates, not a medical assessment or diagnosis. Body composition equations carry errors of several percentage points, and healthy ranges vary with age, ethnicity, muscularity and medical history. Discuss weight or body composition goals with a qualified clinician or dietitian.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

These figures are population-average estimates, not a medical assessment or diagnosis. Body composition equations carry errors of several percentage points, and healthy ranges vary with age, ethnicity, muscularity and medical history. Discuss weight or body composition goals with a qualified clinician or dietitian.

Frequently Asked Questions

Is all lean mass muscle?

No. Bone is about 15% of lean mass and organs another 20-25%, which is why muscle mass is always well below lean mass.

How much muscle can be gained?

Roughly 0.5-1 kg a month for a novice trainee, falling to a few kilograms a year after the first couple of years.

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