Lean Body Mass Calculator: Boer, James & Hume Formulas
Uncover your true body composition by estimating your muscle, bone, and organ mass. Our LBM Calculator uses multiple scientific formulas to help you track fitness progress, optimize nutrition, and gain deeper insights into your health.
What is Lean Body Mass (LBM)?
Lean Body Mass (LBM) represents the total weight of your body minus all the weight from fat mass. LBM includes the weight of your bones, muscles, organs, skin, and water. It is a more accurate measure of your body's metabolic activity than total body weight or BMI.To better understand your fat distribution, you can also check your RFM (Relative Fat Mass) using our dedicated calculator.
Unlike Body Mass Index (BMI), which can misclassify muscular individuals as overweight, LBM provides a clearer picture of your health. Tracking it is essential for athletes looking to gain muscle and for individuals aiming to ensure they lose fat, not muscle, during weight loss.
Fig 1: LBM includes all non-fat components, making it a powerful metric for health and fitness.
What’s a Healthy Lean Body Mass (LBM) Percentage? A Complete Age & Gender Breakdown
| Group | Average LBM (% of body weight) |
|---|---|
| Men 20–39 yr | 75–85% |
| Women 20–39 yr | 65–75% |
| Men 40–59 yr | 70–80% |
| Women 40–59 yr | 60–70% |
| Adults 60+ yr | −1% LBM per year if inactive |
Important factors affecting LBM
- Sex: Men typically have a higher percentage of LBM than women. For example, for adults aged 20-39, the average LBM for men is 75–85%, while for women it is 65–75%.
- Age: After age 30, LBM tends to decline by about 3% to 8% per decade, especially without regular resistance training.
- Genetics: Individual genetic factors can influence your body composition and LBM.
- Activity Level: Athletes, particularly those who do resistance training, typically have higher LBM percentages, ranging from 80% to 90%. A healthy, non-athletic adult generally falls in the 65% to 75% range.
How to calculate lean body mass ?
Our calculator uses several well-established formulas to estimate LBM based on your weight, height, and sex. Since each formula was developed using different research populations, they provide a valuable range rather than a single absolute number. For clinical applications such as nutrition planning or medication dosing, you may also find our Adjusted Body Weight Calculator useful.
Men: LBM = 0.407 × W(kg) + 0.267 × H(cm) - 19.2
Women: LBM = 0.252 × W(kg) + 0.473 × H(cm) - 48.3
Men: LBM = (0.32810 × W(kg)) + (0.33929 × H(cm)) - 29.5336
Women: LBM = (0.29569 × W(kg)) + (0.41813 × H(cm)) - 43.2933
Men: LBM = 1.1 × W(kg) - 128 × (W(kg) / H(cm))²
Women: LBM = 1.07 × W(kg) - 148 × (W(kg) / H(cm))²
How to Use the LBM Calculator
Step 01
Select Your Sex and Unit System
Choose 'Male' or 'Female' and whether you prefer Metric (kg, cm) or Imperial (lbs, ft/in) units.
Step 02
Enter Your Weight, Height, and Age
Input your current body weight, height, and age into the respective fields. Ensure you use positive, realistic numbers.
Step 03
Click 'Calculate LBM'
Press the button to instantly see your estimated Lean Body Mass across multiple recognized formulas.
Step 04
Review Your Results
The calculator will display your LBM values, your LBM as a percentage of total weight, and a visual guide to help you interpret your body composition.
It's deliberate to present results from various formulas. Each was derived from different data sets, so presenting a range gives a genuine impression of scientific reality and avoids false precision.
- Boer, Hume, & James formulas are calculated automatically.
- Direct Body Fat Method: If you enter your body fat %, it calculates LBM = Weight × (1 − BF%).
- Prompts: For users with a high BMI, who are pregnant, highly active, or elderly, the app notes the potential for inaccuracy and suggests considering a professional test.
Why Lean Body Mass Matters
How to Increase Lean Body Mass
Building LBM requires a strategic combination of resistance training and nutrition.
- Resistance Training: Engage in strength training 3-5 times a week, focusing on compound exercises like squats, deadlifts, and presses. Progressive overload (gradually increasing weight or reps) is key to stimulating muscle growth.
- Adequate Protein Intake: Protein provides the building blocks for muscle. Aim for 1.6 to 2.2 grams of protein per kilogram of body weight, spread throughout the day.
- Sufficient Calorie Intake: To build muscle, you need to consume slightly more calories than you burn. A modest surplus provides the energy required for muscle repair and growth.
- Prioritize Sleep and Recovery: Muscles grow during rest. Aim for 7-9 hours of quality sleep per night and include rest days in your training schedule to allow your body to recover.
Fig 2: Calculators are excellent for tracking trends, while DEXA scans provide clinical-grade accuracy.