Skeletal Muscle Mass Calculator

Utilize this skeletal muscle mass calculator to estimate and compare your skeletal muscle mass with your overall body mass, lean body mass, and body fat. This tool can help evaluate your total body composition.

Input your body parameters into the calculator. Also include your body fat percentage, if available. If not, you can use this website's Body Fat Calculator tool to get an estimate and then come back to this page. If you leave the field empty, the calculator will estimate the percentage based on average values for someone of your height, age, and weight who leads a sedentary lifestyle.

Understanding Skeletal Muscle

Lean and muscle mass are often used interchangeably but refer to different body composition components. Lean mass is the total weight of your body minus all the fat. It encompasses muscles, bones, organs, skin, and body water, essentially everything in the body that isn't fat.

Muscle mass refers explicitly to the weight of muscles in the body and is a subset of lean mass. It includes all the muscles in the body, such as skeletal muscles, cardiac muscles, and smooth muscles found in organs.

Smooth muscle, found in internal structures such as the digestive tract and blood vessels, performs complex, involuntary functions. They are arranged in layered sheets that contract in waves, responsible for moving waste through the intestines and helping the lungs expand during breathing.

The cardiac muscle is specific to the heart and contracts and relaxes without conscious awareness. It makes up the middle layers of the heart and is responsible for pumping blood through the cardiovascular system.

Skeletal muscle, which is attached to bones, empowers you with the ability for voluntary movement. It is part of the musculoskeletal system and works with bones, tendons, and ligaments to support body weight and facilitate movement. Skeletal muscles are most visible when there is no fat layer covering them.

In contrast to cardiac and smooth muscles, skeletal muscles are under voluntary control, meaning you can consciously decide to move them. Skeletal muscles can undergo hypertrophy, which is increased muscle size due to exercise, particularly resistance training. Skeletal muscle fibers can increase in size and number of myofibrils, the contractile units of muscle cells.

When you engage in strength training, skeletal muscles respond by repairing and growing stronger. This adaptation is driven by mechanical stress, metabolic stress, and muscle damage, which stimulate muscle protein synthesis.

Skeletal muscle's ability to be voluntarily controlled and its structural capacity for growth and adaptation make it the only muscle type that can be developed through targeted exercise.

Skeletal Muscle Mass Averages

A study published in 2000 in the Journal of Applied Physiology establishes reference data for skeletal muscle mass (SM). The study used a whole-body magnetic resonance imaging protocol to examine how age, sex, body weight, and height affect skeletal muscle mass and distribution in 468 individuals. Part of the results of the study are shown in the table below.

The table shows skeletal muscle mass (SM) as a percentage of total body mass. It presents the SM percentage ranges categorized by age groups and provides the overall averages. Specifically, it shows all age average skeletal muscle percentage for females as 30.6%, and for males as 38.4%.

About this Calculator

This calculator uses formulas developed from a study that examined the relationships between body size, age, and skeletal muscle mass [4]. The study examined the individual and combined effects of weight, height, waist circumference, and age on SM prediction in a large sample of 12,330 individuals from a National Health and Nutrition Survey (NHANES).

Skeletal muscle mass was measured using dual-energy X-ray absorptiometry (DXA). A prediction equation based on resonance imaging was used to calculate the total skeletal muscle mass of the body from the lean tissue mass measured in the arms and legs.