Calculate your lean body mass (muscle, bone, organs — everything except fat) using the Boer formula.
A Lean Body Mass Calculator estimates the total weight of everything in your body except stored fat, including muscle, bone, organs, and water. This measurement provides a more precise picture of body composition than total body weight alone, useful for athletes, bodybuilders, and anyone tracking fitness progress who wants to distinguish between muscle changes and fat changes.
A commonly used formula is the Boer formula: for men, Lean Body Mass = 0.407 × weight (kg) + 0.267 × height (cm) − 19.2; for women, Lean Body Mass = 0.252 × weight (kg) + 0.473 × height (cm) − 48.3. Other formulas like Hume and James use slightly different coefficients, which is why results can vary modestly depending on which specific formula is applied.
Enter your height, weight, and gender. The calculator returns your estimated lean body mass along with the corresponding estimated fat mass (total weight minus lean body mass), giving you a fuller picture of your body composition beyond simple total weight.
Example 1: A man who is 175 cm tall and weighs 80 kg has an estimated lean body mass of 0.407×80 + 0.267×175 − 19.2 ≈ 60.6 kg, meaning roughly 19.4 kg is estimated fat mass.
Example 2: A woman who is 165 cm tall and weighs 65 kg has an estimated lean body mass of 0.252×65 + 0.473×165 − 48.3 ≈ 46.3 kg, meaning roughly 18.7 kg is estimated fat mass.
Total weight doesn't distinguish between muscle gain and fat loss, both of which can cause the scale to move in confusing directions, while tracking lean body mass separately provides clearer insight into whether fitness changes are coming from muscle or fat.
Formula-based estimates provide a reasonable general approximation but are less precise than direct measurement methods like DEXA scans, since formulas rely only on height, weight, and gender without accounting for individual variation in actual body composition.
Men and women have different average proportions of muscle, bone density, and essential fat, so separate formulas with different coefficients better reflect these typical biological differences between the sexes.
Some protein intake guidelines recommend basing targets on lean body mass rather than total body weight, since it's primarily lean tissue (particularly muscle) that drives protein requirements, making this a more physiologically relevant basis for very lean or very heavy individuals.
Yes, if muscle mass increases while fat mass decreases by a similar amount, total weight can remain unchanged on the scale while lean body mass actually increases, which is exactly the kind of favorable body composition shift that weight alone would fail to capture.
Lean body mass, particularly muscle tissue, naturally tends to decline gradually with age unless actively maintained through resistance exercise and adequate protein intake, a process called sarcopenia that becomes an increasingly important health consideration in older adults.
Since maximizing muscle gain while minimizing fat gain is a core goal in bodybuilding, tracking lean body mass changes over time provides more actionable feedback for adjusting training and nutrition than simply watching total body weight fluctuate.
Yes, lean body mass encompasses everything that isn't stored fat, including bone, muscle, organs, connective tissue, and body water, making it a broader category than muscle mass alone, though muscle typically represents the largest and most variable component.
Consistent resistance training combined with adequate protein intake and sufficient overall calories (particularly during a muscle-building phase) is the primary evidence-based approach for increasing lean body mass, since muscle tissue specifically requires this combination of mechanical stimulus and nutritional support to grow.
Rather than setting a total weight loss target, some approach weight management by focusing on preserving or growing lean body mass while reducing fat mass, since this body composition-focused approach often better reflects genuine health and fitness improvement than total weight alone.
Since body water is included within lean body mass, significant dehydration or fluid retention can temporarily shift calculated lean body mass figures, which is why measuring at a consistent time and hydration state improves the reliability of tracking changes over time.