Input parameters
Results
Enter your details above and select “Calculate skeletal muscle mass” to view detailed results, including skeletal muscle mass, index, and comparison estimates.
Example data table
These example cases illustrate how the equation behaves for different ages, heights, resistance values, and measurement systems. Values are approximate and for demonstration only.
| Case | System | Gender | Age (years) | Height | Weight | Resistance (ohms) | Estimated skeletal muscle mass (kg) |
|---|---|---|---|---|---|---|---|
| Example 1 | Metric | Male | 30 | 180 cm | 80 kg | 500 | Approx. 34 |
| Example 2 | Metric | Female | 45 | 165 cm | 65 kg | 550 | Approx. 24 |
| Example 3 | Imperial | Male | 65 | 68 in | 154 lb | 600 | Approx. 26 |
Formula used in this calculator
The primary estimate uses a widely cited bioelectrical impedance equation developed from magnetic resonance imaging data. It relates skeletal muscle mass to height, resistance, age, and gender.
The equation is:
Skeletal muscle mass (kg) = (height2 / resistance × 0.401) + (gender factor) + (age × -0.071) + 5.102
- Height is in centimeters (cm).
- Resistance is in ohms, measured by a bioimpedance device.
- Gender factor is 3.825 for males and 0 for females.
- Age is in years.
The calculator also reports a skeletal muscle mass index (SMMI), defined as skeletal muscle mass (kg) divided by height squared in meters (kg/m2), often used in research and clinical screening.
An optional simple estimate converts total muscle mass percentage from a body composition scale into muscle mass in kilograms by multiplying body weight by the reported percentage.
How to use this skeletal muscle mass calculator
- Choose your gender from the dropdown list.
- Enter your age in years.
- Select your preferred measurement system. Use centimeters and kilograms for the metric option, or inches and pounds for the imperial option.
- Enter your height and body weight in the fields that match your chosen system. The other set of fields can be left blank.
- Enter the bioelectrical impedance resistance value from your analyzer or scale. This is typically displayed as “R” or “resistance” in ohms.
- If your device also reports muscle mass percentage, optionally enter that value to compare with the impedance-based skeletal muscle mass estimate.
- Click the calculate button to generate skeletal muscle mass and index values.
- Review the numerical results, including percentage of body weight and non-diagnostic interpretation, and compare them with the example data table if desired.
- Use the CSV button to export results and example cases for spreadsheets, or the PDF button to download a summary report for documentation.
This tool is for educational and research support only and does not replace professional medical assessment, diagnosis, or treatment. Always discuss concerns with a qualified clinician.
Understanding skeletal muscle mass
Skeletal muscle mass represents the contractile tissue attached to bones that generates movement, stabilizes joints, and supports posture. It is distinct from smooth and cardiac muscle and is a major reservoir of amino acids, glycogen, and metabolic activity in the body.
Skeletal muscle and total body mass
In healthy adults, skeletal muscle often contributes 30–40% of total body mass, with higher proportions in resistance-trained individuals. Comparing muscle mass from this calculator with body weight helps identify whether low mass reflects generalized underweight, selective muscle loss, or measurement variability.
Muscle chemistry, proteins, and amino acids
Skeletal muscle tissue is rich in structural and contractile proteins built from amino acids. When analysing protein composition or supplement design, you can pair this tool with an amino acid molecular weight calculator to understand how individual residues contribute to protein mass.
Energy metabolism and muscle tissue
Muscle fibers store glycogen and intramuscular triglycerides, supporting rapid ATP generation during activity. Higher skeletal muscle mass generally increases whole-body glucose disposal and resting energy expenditure, which is why muscle preservation is central in metabolic health, athletic conditioning, and weight management planning.
Muscle mass, creatine, and phosphate stores
Phosphocreatine within skeletal muscle buffers ATP during brief, intense efforts. When formulating creatine dosing strategies, a chemistry tool such as the Mole Mass Converter Calculator helps convert grams of creatine to moles and relate them to estimated muscle mass.
Tracking skeletal muscle change over time
Repeated measurements using the same device, protocol, and hydration status highlight trends in muscle mass. A gradual rise may reflect successful resistance training, whereas a downward trajectory can flag deconditioning, prolonged illness, or inadequate energy and protein intake requiring further assessment.
Muscle mass and functional performance
Higher skeletal muscle mass often correlates with better strength, power, and mobility tests, but quality matters alongside quantity. Combining mass estimates with handgrip strength, sit-to-stand time, or walking speed provides a more complete picture of functional capacity in athletes and clinical populations.
Age-related changes in skeletal muscle
Ageing is associated with progressive loss of muscle mass and strength, sometimes termed sarcopenia. Monitoring skeletal muscle index in older adults helps identify individuals at risk of falls, frailty, and hospitalization so that training, nutrition, and medical interventions can be implemented early.
Hydration, electrolytes, and bioimpedance readings
Bioelectrical impedance assumes relatively stable hydration and electrolyte balance. Dehydration, oedema, or recent heavy exercise can shift resistance values and distort estimated skeletal muscle mass. Whenever possible, schedule readings in similar conditions to improve the reliability of longitudinal comparisons.
Using chemistry calculators with muscle assessments
When converting between nutrient doses, supplement compositions, and tissue-level effects, chemistry tools complement muscle estimates. For example, the Molar Mass of Compound Calculator helps translate labelled milligrams of compounds into moles that can be related to muscle uptake.
Frequently asked questions
1. Is this skeletal muscle mass value the same as lean body mass?
No. Lean body mass usually includes organs, water, and other fat-free tissues. This calculator focuses on the skeletal muscle compartment estimated from height, resistance, age, and gender, which is only one component of total lean mass.
2. How often should I re-measure skeletal muscle mass?
For training or lifestyle changes, monthly to quarterly measurements are usually sufficient. In rehabilitation or clinical monitoring, more frequent checks may be appropriate. Always compare results from the same device, protocol, and time of day where possible.
3. Why do results differ from my smart scale or DEXA scan?
Different devices use distinct equations, reference populations, and measurement technologies. This tool is based on a specific bioimpedance equation and provides approximate values. DEXA, CT, and MRI can offer more direct regional assessments in clinical research settings.
4. Can athletes have high muscle mass but still be unhealthy?
Yes. Elevated muscle mass does not guarantee optimal cardiovascular, metabolic, or mental health. Blood pressure, lipid profile, glucose control, sleep, and psychological wellbeing all matter. Interpreting muscle results within a full health assessment is always recommended.
5. Does body fat percentage affect skeletal muscle mass estimates?
Extreme leanness or high adiposity can influence fluid distribution and therefore bioimpedance readings. Although the equation focuses on height, resistance, age, and gender, interpreting results alongside independent body fat estimates provides a more balanced view of body composition.
6. How can chemistry tools support supplement planning?
When you design supplementation around muscle health, you may need to convert labelled milligrams to moles or compare compound doses. A tool like the Molar Mass of Compound Calculator helps translate between chemical amounts and practical serving sizes.
7. Is this calculator suitable for diagnostic decisions?
No. It is an educational and decision-support aid only. Diagnosing sarcopenia, malnutrition, or endocrine disorders requires clinical evaluation, laboratory data, and sometimes imaging. Always discuss concerning findings or symptoms with a qualified healthcare professional before changing treatment.