Skeletal Muscle Mass Chart: Normal Ranges and How to Read Them

Last updated: June 2026

Skeletal Muscle Mass Chart: Normal Ranges and How to Read Them

Skeletal muscle mass charts come in two forms: percentage-based charts derived from MRI data, and index-based charts that adjust for height and are used clinically to screen for sarcopenia. The index-based charts — using ALMI from DEXA and SMI from BIA — are more useful for comparing yourself to population norms, because they account for the fact that taller people naturally carry more muscle. Here’s how to read each type and what the numbers mean.

The Two Main Metrics to Know

ALMI (Appendicular Lean Mass Index) — measured by DEXA scan. This is the gold-standard metric for skeletal muscle status:

ALMI = (Arm lean mass + Leg lean mass) ÷ Height² (kg/m²)

SMI (Skeletal Muscle Index) — estimated by BIA devices. Used when DEXA isn’t available:

SMI = Total estimated skeletal muscle mass ÷ Height² (kg/m²)

Both metrics are expressed in kg/m² and allow comparison across people of different heights. ALMI (DEXA) and SMI (BIA) are not interchangeable — they use different measurement methods and produce different absolute values. Always compare ALMI values against DEXA-based charts, and SMI values against BIA-based charts.

Female ALMI Percentile Chart (DEXA-Based)

Based on over 450,000 DEXA scans, the following table shows female ALMI by age group and percentile. Your percentile tells you how your appendicular muscle mass compares to other women of the same age:

All values in kg/m². Source: BodySpec DEXA database (>450,000 scans). Clinical low muscle mass threshold for women: ALMI <5.5 kg/m².

For men, the DEXA-based low muscle mass threshold is ALMI <7.26 kg/m² (BodySpec reference) and <7.0 kg/m² (EWGSOP2 clinical guidelines). A DEXA scan that includes ALMI will position you against these reference values directly.

BIA Normative Values: Absolute Skeletal Muscle Mass by Age

When a DEXA scan isn’t available, BIA-based measurements from large population studies provide useful reference values. The following data comes from a study of 18,625 adults published in Frontiers in Public Health. These are median absolute skeletal muscle mass values (in kilograms) by age group — not adjusted for height, so they are most useful as general benchmarks:

Women — Median Skeletal Muscle Mass (BIA)

Men — Median Skeletal Muscle Mass (BIA)

Note that absolute muscle mass peaks in the 30–49 age range for both sexes, then declines more steeply from 60 onward. Men’s absolute muscle mass runs approximately 10–12 kg higher than women’s across all age groups.

Sarcopenia Thresholds

Both DEXA and BIA have established clinical thresholds for low skeletal muscle mass associated with sarcopenia risk:

DEXA thresholds from EWGSOP2 (2018). BIA thresholds from EWGSOP2 BIA-specific cut-offs.

BIA SMI thresholds are substantially higher than DEXA ALMI thresholds because BIA estimates total skeletal muscle mass (whole body), while DEXA ALMI measures only appendicular (limb) lean mass. Comparing a BIA-derived SMI against a DEXA ALMI threshold — or vice versa — will produce incorrect conclusions. Always match the metric to its chart.

How to Read a Percentile Chart

Percentile rankings work the same way regardless of the metric:

• Below 10th percentile — low muscle mass; clinical review warranted if accompanied by functional decline or strength loss
• 10th–25th percentile — below average; intervention (resistance training, protein intake) is beneficial
• 25th–75th percentile — normal range for your age group
• 75th–90th percentile — above average; reflects consistent training or favorable genetics
• Above 90th percentile — high muscle mass; typical of dedicated athletes or individuals with substantial long-term training history

Percentile ranking matters more than absolute value. A 65-year-old woman at the 60th percentile for her age group has meaningfully better muscle status than a 30-year-old at the 10th percentile — despite possibly having a lower absolute ALMI number.

Three Caveats Before Using These Charts

1. Match the measurement tool to the chart. BIA readings should be compared to BIA normative values. DEXA readings should be compared to DEXA-based percentile tables. Mixing methods produces misleading comparisons.

2. Hydration affects BIA readings significantly. A 1–2% change in hydration can shift a BIA skeletal muscle estimate by 1–2 kg. A single BIA reading taken without consistent pre-test conditions is not reliable enough to position against population norms. Track the trend across multiple consistent measurements instead.

3. Track trends, not snapshots. Whether you’re above or below the median matters less than whether your muscle mass is stable, increasing, or declining over time. A baseline DEXA scan now gives you a reference point to compare against in 6 or 12 months — that change matters more than where you start.