What Is a Good Muscle Mass Percentage? Charts for Men and Women

Last updated: June 2026

What Is a Good Muscle Mass Percentage? Charts for Men and Women

A good muscle mass percentage for men aged 18–35 is roughly 33–39% of total body weight. For women in the same age range, 24–31% is typical. But these numbers shift with age and depend entirely on how muscle mass is being measured — a BIA smart scale and a DEXA scan produce different figures because they measure different things. Here are the reference ranges by age and sex, and what they actually mean.

Muscle Mass Percentage Chart for Men

These ranges are based on MRI population data and DEXA scan reference databases. They represent typical and above-average muscle mass percentages relative to total body weight:

Population-level MRI data puts the average skeletal muscle mass for men at approximately 38.4% of body weight — in the upper end of the “average” range above. Men naturally carry more muscle than women due to higher testosterone levels.

Muscle Mass Percentage Chart for Women

Women average approximately 30.6% skeletal muscle mass based on the same MRI dataset. The 8-percentage-point gap between men and women reflects biological differences in testosterone, not a deficiency in women’s health or fitness.

Why Your Reading May Differ from These Charts

The charts above are based on MRI and DEXA measurements. If you’re using a BIA smart scale (such as a Fitbit, Withings, or Garmin scale), the number it reports is an estimated skeletal muscle mass calculated from your body’s electrical resistance — and it uses a different formula than DEXA. BIA devices tend to overestimate skeletal muscle mass compared to DEXA, so your BIA reading may sit higher than the ranges above. This doesn’t mean you’re doing better; it means the measurements aren’t directly comparable.

What matters more than hitting a specific percentage is:

• Tracking the trend over time using the same measurement method
• Ensuring muscle mass is not declining with age faster than expected
• Checking appendicular lean mass index (ALMI) via DEXA for clinical accuracy

The Clinical Measure That Actually Matters: ALMI

Clinicians don’t use percentage of total body weight to screen for low muscle mass. They use Appendicular Lean Mass Index (ALMI) — measured by DEXA — because it accounts for body size and focuses on the most functionally important muscle (arms and legs):

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

Sarcopenia thresholds (EWGSOP2 guidelines):

• Men: ALMI <7.0 kg/m² (low muscle mass)
• Women: ALMI <5.5 kg/m² (low muscle mass)

These cut-offs are not about appearance or fitness — they signal a level of muscle loss associated with significantly increased risk of falls, fractures, hospitalization, and all-cause mortality.

What Low Muscle Mass Means for Your Health

Falling below the “low” thresholds in the charts above — or below the ALMI clinical cut-offs — carries concrete health consequences that go well beyond how you look or perform in the gym:

• Sarcopenia: Age-related muscle loss that becomes self-accelerating once it passes a threshold — less muscle → less movement → less stimulus for muscle maintenance → faster loss
• Insulin resistance: Skeletal muscle is responsible for approximately 70–80% of post-meal glucose clearance. Low muscle mass significantly impairs blood sugar regulation and increases type 2 diabetes risk
• Slower metabolism: Muscle burns 4.5–7 calories per pound at rest. Less muscle means a lower baseline metabolic rate, making body fat accumulation more likely over time
• Cardiovascular risk: Several large studies have associated low skeletal muscle mass with higher rates of cardiovascular mortality, independent of body fat levels
• Higher all-cause mortality: Muscle mass and grip strength are among the strongest physical predictors of lifespan in older adults — more consistently predictive than BMI

How to Improve Your Muscle Mass Percentage

Improving muscle mass percentage requires either gaining muscle, losing fat, or both. The most effective levers:

• Resistance training 2–4 times per week — compound movements with progressive overload (adding weight, reps, or sets over time). Each muscle group should be trained at least twice weekly
• Protein intake of 1.4–2.0 g/kg body weight daily — distributed across 3–4 meals with 20–40g per meal to sustain muscle protein synthesis throughout the day
• Calorie management — a modest surplus (10–15% above TDEE) supports muscle growth; a deficit can improve muscle percentage if protein is high enough to preserve lean mass during fat loss
• Sleep 7–9 hours — muscle repair and growth hormone release peak during sleep; chronic sleep deprivation accelerates muscle loss and impairs recovery

For adults over 50, the priority shifts from building maximum muscle to preventing loss. Even modest resistance training — 2 sessions per week — significantly slows sarcopenia and maintains functional independence.

Frequently Asked Questions

Is 40% muscle mass good for a man?

For men under 55, 40% or above is in the “good” to “athletic” range. For men over 55, 40% would be exceptional. Whether this is achievable depends significantly on training history and body fat level — gaining muscle and reducing fat both move the percentage upward.

Is 30% muscle mass good for a woman?

For women 18–35, 30% is in the average range. For women 36–55, 30% is in the upper-average to “good” bracket. For women 56–75, 30% is above average. Context matters — 30% achieved through consistent resistance training is more functional than 30% from a naturally lean frame with minimal muscle.

Why does my smart scale read higher than these charts?

BIA smart scales estimate skeletal muscle mass using electrical resistance equations calibrated to specific populations. Most BIA devices overestimate skeletal muscle mass compared to DEXA by approximately 2.5%. The charts above are based on MRI and DEXA data, so BIA readings will often appear higher than these reference ranges even when actual muscle mass is within normal bounds.