SMM/WT
Skeletal Muscle Mass to Weight (SMM/WT)
This value shows what share of your total body weight is made up of skeletal muscle mass.
Short answer
The muscle share mirrors percent body fat. During weight reduction it works as a check that the loss is coming more from fat than from muscle — but always confirm it against absolute muscle mass.
What the value represents
Where the muscle index relates muscle to height, this value relates it to weight. It answers how large a part of what you weigh is skeletal muscle.
Because it is a share, it moves from two sides in the same way percent body fat does. It rises when muscle is added, but also when fat is lost and muscle stays where it was.
It is the counterpart of percent body fat — both describe the composition of the same weight from opposite sides.
- The share of total body weight made up of skeletal muscle mass.
- A companion to percent body fat, showing the muscle side of the same balance.
- It does not represent strength, performance or how muscle is distributed.
How the value is produced
- A calculated value from skeletal muscle mass and measured weight.
- Skeletal muscle mass is an estimate from bioimpedance; weight is directly measured.
- The result sheet accompanies it with Z-scores and T-scores against the manufacturer reference set.
How to read the current value
- Read it alongside percent body fat. When one rises and the other falls, you are usually looking at the same change described from both sides.
- The Z-score and T-score describe your position relative to the manufacturer data set, not to a clinical norm.
- The share alone does not establish whether your muscle mass is sufficient — the muscle index related to height and age is what serves that purpose.
- The manual does not publish a recommended band for this ratio, so treat it as a relative measure rather than a target.
How to read change over time
- A rising share at stable weight means composition is shifting: muscle is being added while something else is being lost.
- A rising share with falling weight usually means the loss came more from fat than from muscle. During a reduction that is the desirable situation.
- A falling share during weight reduction signals that muscle is going too. It is worth confirming against the absolute muscle mass in kilograms.
General principles: how to read change between measurements →
What to read it with
- Skeletal Muscle Mass in kilograms – the absolute value behind the share.
- Percent Body Fat – the mirror value of the same balance.
- Weight – without it a change in the ratio cannot be interpreted.
- Skeletal Muscle Index – the same muscle related to height instead of weight.
Common misunderstandings
- The muscle share is not the same as the muscle index. They differ in the denominator: weight instead of height squared.
- A higher share does not automatically mean more muscle in kilograms — it can simply mean weight went down.
- The value says nothing about muscle strength.
What can affect the result short term
- Hydration, which affects the estimate of muscle mass.
- Food and drink before the measurement, because they change the weight in the denominator.
- Training shortly before the measurement.
What to do next
- When you are tracking weight reduction, use this share as a check that muscle is not being lost.
- Always look up muscle mass in kilograms alongside it — that distinguishes a change in the numerator from a change in the denominator.
- For comparison against an age group, reach for the muscle index rather than this share.
What the value does not determine
- It does not measure muscle strength or function.
- The share changes even without a real change in muscle mass.
- The reference scores come from a manufacturer data set.
In more depth, with sourcesIn more depth: share versus index, and what each one capturesExpand the detailed explanation
Relating muscle mass to weight and relating it to height answer two different questions. The share of weight describes current body composition and is sensitive to any change in weight, including changes in the fat component. The height-based index is robust to changes in weight and serves comparison against an age group.
The practical consequence is that during weight reduction the muscle share increases even when the absolute amount of muscle falls slightly — it is enough for fat to fall faster. That is why the share should never be read without the absolute muscle mass in kilograms.
The Z-scores and T-scores reported for this value come from the manufacturer reference set and serve orientation inside the InBody ecosystem. They are not clinical norms and cannot be compared with scores from other methods.
Sources
- InBody 970 Result Sheet Interpretation (ENG_A_211104) — InBody Co., Ltd.
On this page
Related values
Related articles
Where to find it
The Muscle-Fat Analysis bar chart and the Obesity Analysis section that follows it.
- Reviewed by
- MojeInBody content team
- Date
An InBody measurement is not a diagnostic tool. Results do not determine health status and do not replace a medical examination.
FAQ
Frequently asked questions
Answers to what people ask most often about this value.
My muscle share is rising but my muscle mass in kilograms is falling. What does that mean?
It means weight is falling faster than muscle mass — so the loss is coming predominantly from fat. The share rises even though the absolute amount of muscle dipped slightly.
Explanations make the most sense alongside your own trend.
The public guide is open to everyone. The client portal adds your own value, history and the context of a specific measurement.