In gyms, health apps, and wellness conversations around the world, people often talk about gaining muscle or improving body composition. But a simple question remains surprisingly difficult to answer: how much muscle mass should a healthy person actually have?

While many fitness enthusiasts focus on building muscle for appearance or athletic performance, experts say muscle mass plays a far more important role. From supporting mobility to protecting long-term health, maintaining muscle is increasingly recognized as a key marker of overall well-being.

Understanding Muscle Mass

To understand muscle mass, it helps to start with the bigger picture of body composition.

The human body is generally divided into two main components: body fat and lean body mass. Lean body mass includes everything in the body that isn’t fat—such as muscles, bones, organs, water, and skin.

Muscle mass specifically refers to the weight and size of muscle tissue, particularly skeletal muscle, which controls movement and posture. These muscles help people walk, lift objects, maintain balance, and perform everyday activities.

Although the terms “lean body mass” and “muscle mass” are often used interchangeably, they are not the same. Muscle mass is just one component of lean mass.

What Research Says About Average Muscle Mass

There is currently no universal guideline for the “ideal” amount of muscle mass a person should have. However, research offers some useful benchmarks.

On average, skeletal muscle accounts for about 40 percent of total body weight. Studies examining adult populations have also found differences between men and women, as well as changes across age groups.

Among men aged 18 to 35, muscle mass typically ranges from about 40 to 44 percent of body weight. For women in the same age group, the average range is 31 to 33 percent.

These percentages tend to decline gradually with age, reflecting a natural process known as sarcopenia, or age-related muscle loss. Beginning around age 40, adults may lose as much as 8 percent of muscle mass per decade if preventive measures are not taken.

Measuring Muscle Mass Isn’t Simple

Despite the growing interest in body composition, measuring muscle mass precisely remains challenging.

The most accurate tools—such as MRI scans, CT scans, or dual-energy X-ray absorptiometry (DEXA)—are expensive and usually available only in clinical or research settings.

Other techniques, including bioimpedance scales, hydrostatic weighing, skinfold measurements, or waist and hip calculations, can provide estimates of body composition. While these methods are more accessible in gyms or at home, their results are less precise.

For many people, health professionals recommend focusing on body fat percentage and overall physical function rather than attempting to calculate exact muscle mass.

Why Muscle Matters for Long-Term Health

Maintaining healthy muscle levels is important for far more than physical appearance.

Low muscle mass has been associated with several health conditions, including diabetes, heart disease, obesity, osteoporosis, and increased risk of injury. Reduced muscle strength can also affect balance and mobility, increasing the likelihood of falls later in life.

On the other hand, higher muscle mass is linked to better metabolic health, improved physical performance, and a lower risk of chronic disease.

Emerging research also suggests muscle strength may play a role in cognitive health and mental well-being, though more studies are needed to fully understand the connection.

Building and Preserving Muscle

Experts agree that two factors are essential for maintaining muscle mass: regular exercise and proper nutrition.

Strength training—such as lifting weights, using resistance bands, performing bodyweight exercises, or participating in high-intensity interval workouts—stimulates muscles to grow and adapt. Health guidelines typically recommend at least two strength-training sessions per week targeting major muscle groups.

Nutrition is equally important. Protein supports muscle repair and growth, while carbohydrates provide the energy needed for workouts. Whole foods rich in vitamins, minerals, and healthy fats help maintain overall muscle function.

For people working long office hours or spending much of the day seated, even small lifestyle adjustments—such as walking breaks, resistance exercises at home, or structured gym sessions—can help maintain muscle health.

The Bottom Line

While there is no single “perfect” muscle mass target, maintaining strong, healthy muscles is a key component of long-term wellness.

Rather than focusing solely on the number on a scale, experts suggest paying attention to strength, mobility, and body composition. With consistent exercise and balanced nutrition, building and preserving muscle can support better health well into later life.