Calculator Form
Formula Used
This calculator uses a common bioelectrical impedance based estimate for skeletal muscle mass. It is suitable for educational estimation and quick screening workflows.
SMM (kg) = [((Height in cm² / Resistance in ohms) × 0.401) + (Sex × 3.825) + (Age × -0.071) + 5.102] × Adjustment Factor
Where:
Sex = 1 for male, 0 for female
Adjustment Factor = 1 + (Adjustment% / 100)
SMI (kg/m²) = SMM / Height in meters²
Muscle % = (SMM / Body Weight) × 100
The result depends strongly on consistent BIA measurement conditions, device quality, hydration state, and body composition method.
How to Use This Calculator
- Choose sex and enter age.
- Enter height and select centimeters or inches.
- Enter body weight and select kilograms or pounds.
- Enter resistance from a body impedance device.
- Apply an optional percent adjustment if your workflow needs it.
- Press calculate to see the result above the form.
- Review skeletal muscle mass, index, percentage, and chart output.
- Use the CSV or PDF buttons to download the result.
Example Data Table
| Case | Sex | Age | Height | Weight | Resistance | Estimated SMM | SMI |
|---|---|---|---|---|---|---|---|
| Sample A | Male | 32 | 175 cm | 78 kg | 450 Ω | 33.95 kg | 11.08 kg/m² |
| Sample B | Female | 29 | 162 cm | 61 kg | 520 Ω | 23.28 kg | 8.87 kg/m² |
| Sample C | Male | 47 | 180 cm | 92 kg | 560 Ω | 28.79 kg | 8.89 kg/m² |
Important Notes
- Use the same device and measurement timing for better comparisons.
- Avoid comparing results taken under very different hydration conditions.
- This page is not a substitute for clinical assessment.
- Interpretation bands here are general, not diagnostic thresholds for every population.
FAQs
1) What does skeletal muscle mass mean?
Skeletal muscle mass is the estimated weight of muscles attached to the skeleton. These muscles support movement, posture, force production, and daily physical function.
2) Does this calculator diagnose low muscle conditions?
No. This tool gives an estimate for educational use. Diagnosis requires validated assessments, clinical history, strength testing, function measures, and professional judgment.
3) Why is resistance needed here?
Resistance is the electrical opposition measured by a bioimpedance device. It helps estimate body compartments because lean tissues conduct current differently from fat tissue.
4) Why do hydration changes matter?
Hydration affects impedance readings. If hydration changes, resistance may shift, and the estimated skeletal muscle mass may move even when true muscle tissue has not changed.
5) What is skeletal muscle index?
Skeletal muscle index, or SMI, adjusts estimated muscle mass for height. It helps compare body size differences more fairly than raw muscle mass alone.
6) Can I use pounds and inches?
Yes. The form accepts pounds and inches, then converts them internally before calculation. This keeps the estimate consistent while supporting different unit preferences.
7) What does the adjustment field do?
The adjustment field applies a simple percentage increase or decrease to the estimate. It is useful when you want to test sensitivity or align with an internal workflow.
8) What should I do with repeated results?
Focus on trends collected under similar conditions. A series of measurements often gives more practical insight than one isolated estimate taken on a single day.