Estimate lean body mass using sex, height, and weight. The result represents non-fat body components, including muscle, bone, organs, connective tissue, and water in total.
Result = Validated health or fitness equation applied to the measurements and options entered. Review the methodology and limitations before interpreting the estimate.The estimate uses the requested body measurements and the equation identified in the formula section. Measurement technique, body composition, age, sex selection, hydration, pregnancy and medical conditions can affect interpretation.
The Lean Body Mass Calculator estimates how much of your body weight consists of everything other than stored body fat. Lean body mass includes muscle, bone, organs, connective tissue, and body water. The calculator typically uses your sex, height, and weight to produce an estimate in pounds or kilograms. This result can provide context for body-composition tracking, fitness planning, and weight changes, but it does not directly measure muscle mass or diagnose your health. Formula-based estimates may differ from results obtained through clinical body-composition testing.
Enter current measurements rather than a target weight or an older measurement. If you are comparing results over time, use the same formula, units, scale, and measurement conditions for each calculation.
The calculator applies an established prediction equation to your height, weight, and sex. It estimates the combined weight of the body’s non-fat components rather than measuring each component separately.
Lean body mass is often described using the following relationship:
Lean body mass = Total body weight − Body fat mass
However, when a measured body-fat percentage is unavailable, an equation can estimate lean body mass directly from height and weight. The Boer equations are commonly used for adults. Other recognized methods, including the James and Hume equations, use different coefficients and may produce slightly different results.
Lean body mass should not be confused with skeletal muscle mass. Muscle is one part of lean body mass, along with bones, organs, body water, and other non-fat tissues.
A commonly used method is the Boer formula:
For males:
LBM = (0.407 × W) + (0.267 × H) − 19.2
For females:
LBM = (0.252 × W) + (0.473 × H) − 48.3
Where:
If measurements are entered in U.S. customary units, the calculator must convert pounds to kilograms and feet or inches to centimeters before applying these equations. A result may then be converted back to pounds.
When body-fat percentage has been measured separately, lean body mass can also be calculated as:
LBM = Body weight × (1 − Body-fat percentage ÷ 100)
This second calculation depends heavily on the accuracy of the body-fat measurement and is not interchangeable with a height-and-weight prediction equation.
Consider a male who weighs 176 pounds and is 5 feet 10 inches tall.
Using the Boer formula for males:
LBM = (0.407 × 79.83) + (0.267 × 177.8) − 19.2
LBM = 32.49 + 47.47 − 19.2
LBM = 60.76 kg
Converting the result to pounds:
60.76 kg × 2.20462 = approximately 134.0 lb
The estimated lean body mass is therefore about 60.8 kilograms or 134.0 pounds. The remaining weight is approximately 42 pounds, but that difference should not be treated as a precise clinical measurement of body fat because the lean body mass value itself is formula-based.
Your result represents the estimated weight of all non-fat body components. A larger lean body mass value does not automatically mean that someone is healthier, more muscular, or more physically fit. Height, overall body size, bone mass, body water, organ mass, and muscle mass can all influence the result.
The number is usually most useful when interpreted alongside your total body weight and tracked consistently over time. Even then, small changes may reflect hydration, recent food intake, measurement variation, or differences between formulas rather than an actual gain or loss of tissue.
There is no single ideal lean body mass that applies to every adult. Meaningful interpretation depends on factors such as height, sex, age, body composition, health status, and the purpose of the calculation. Avoid comparing your result directly with someone who has substantially different physical characteristics.
Lean body mass is also different from fat-free mass in some technical contexts. Fat-free mass excludes all extractable fat, while lean body mass may include a small amount of essential fat. General-purpose calculators often use the terms interchangeably, but specialized clinical assessments may distinguish between them.
This calculator provides a mathematical estimate, not a direct assessment of body composition. It cannot determine exactly how much muscle, bone, organ tissue, or body water you have. It also cannot show where body fat is located or distinguish changes in muscle from changes in hydration.
The formula does not diagnose obesity, muscle loss, malnutrition, fluid retention, or any other medical condition. It should not be used by itself to set medication doses, determine treatment, or make significant nutritional or medical decisions.
Accuracy may be reduced for children, adolescents, pregnant people, older adults, competitive athletes, bodybuilders, people with limb differences, and individuals experiencing major fluid shifts or certain medical conditions. These groups may require an appropriately selected assessment method and professional interpretation.
More direct body-composition methods include dual-energy X-ray absorptiometry, air-displacement plethysmography, and professionally administered skinfold or bioelectrical impedance assessments. Each method has its own assumptions and sources of error. Consult a qualified healthcare professional when body composition is relevant to a health concern, diagnosis, treatment plan, or medication decision.
Lean body mass is total body weight minus stored body fat. It includes muscle, bones, organs, connective tissue, body water, and other non-fat components.
No. Skeletal muscle contributes to lean body mass, but the result also includes water, bones, organs, and other tissues. A lean body mass calculator cannot isolate muscle weight.
Accuracy varies by equation and individual characteristics. Height-and-weight formulas are useful for general estimation, but they cannot account fully for differences in muscularity, bone structure, hydration, age, or fat distribution.
Yes. Multiply body weight by one minus the body-fat percentage expressed as a decimal. For example, at 20% body fat, multiply weight by 0.80. The result is only as reliable as the body-fat measurement.
Each formula uses different coefficients and was developed from a particular study population. Differences between results are expected and do not necessarily indicate that one calculation was performed incorrectly.
Actual muscle and bone tissue generally do not change dramatically in one day, but scale weight and measured lean mass can fluctuate because lean body mass includes water. Hydration, meals, sodium intake, and measurement conditions can influence short-term readings.
Measure under consistent conditions, calculate the result and record the date and method. Compare trends only when the same units and measurement technique are used each time.
| Measurement | What It Represents | Important Distinction |
|---|---|---|
| Lean body mass | Muscle, bone, organs, connective tissue, body water, and other non-fat components | It is not a direct measurement of muscle mass. |
| Body fat mass | The estimated weight of stored body fat | It requires a body-fat estimate or a separate assessment. |
| Body-fat percentage | The percentage of total body weight attributed to fat | It is a proportion, while lean body mass is expressed as a weight. |
| Skeletal muscle mass | The estimated weight of muscles attached to the skeleton | It represents only one component of lean body mass. |
| Body mass index | A height-to-weight screening measurement | BMI does not directly separate fat mass from lean mass. |
If total body weight and estimated lean body mass are known, the difference provides an approximate fat-mass value:
Estimated body fat mass = Total body weight − Estimated lean body mass
For example, a person who weighs 176 pounds and has an estimated lean body mass of 134 pounds would have an estimated difference of 42 pounds. Because the lean body mass value comes from a prediction equation, the calculated difference is also an estimate rather than a direct measurement.
Lean body mass can also be expressed as a percentage of total body weight:
Lean body mass percentage = (Lean body mass ÷ Total body weight) × 100
Using the same example:
(134 ÷ 176) × 100 = approximately 76.1%
This means approximately 76.1% of the person’s body weight is estimated to consist of lean tissue and body water. It does not mean that 76.1% of the body is muscle.
General prediction equations may provide less representative results for people with unusually high muscularity, very low or high body weight, substantial fluid retention, limb differences, pregnancy-related body changes, or physical characteristics that differ from the population used to create the formula.
Children and adolescents also require age-appropriate assessment methods. If lean body mass is needed for clinical nutrition, medication dosing, recovery monitoring, or management of a medical condition, use the method specified by an appropriately qualified healthcare professional.
Confirm that both results were calculated with the same formula and measurement units. A Boer result should not be compared directly with a James, Hume, bioelectrical impedance, or imaging-based result as though all methods measure body composition identically. Differences may reflect the assessment method rather than a genuine physical change.