Lean Body Mass (LBM) Calculator
Calculate your lean body mass (LBM) in kg and lb using the Boer formula. Get fat mass, body fat %, and lean mass % instantly — used for protein targets and drug dosing.
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Reviewed by: Martín Rodríguez (editorial policy ) · Last reviewed:
Result
Lean Body Mass (kg)
Lean Body Mass (lb)
Fat Mass (kg)
Fat Mass (lb)
Lean Mass %
Body Fat %
Formula Applied
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For guidance only — not medical advice. Consult a licensed healthcare professional.
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Lean body mass (LBM) is everything your body weighs except fat — muscles, bones, organs, water, and connective tissue. Knowing your LBM matters for accurate medication dosing (many drugs are dosed per kg of LBM), setting daily protein targets, and tracking fitness progress without the noise of fat fluctuation. This calculator uses the Boer formula (1984), a widely cited clinical reference validated across a broad range of adult body sizes and derived from direct cadaver analysis.
When to use this calculator
- Calculating weight-based medication or anesthesia doses that reference lean body weight
- Setting daily protein intake targets (typically 1.6–2.2 g per kg of LBM for active adults)
- Tracking muscle gain vs. fat loss over a training or diet program
- Estimating body fat mass when a DEXA scan or hydrostatic test isn't available
- Assessing nutritional status in clinical or sports medicine settings
- Comparing lean mass percentage before and after a body recomposition phase
Body Fat % Reference Ranges by Category — Men vs. Women
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Acceptable | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Fuente: American Council on Exercise — Percent Body Fat Norms (ACE, 2024)
How it works
What is Lean Body Mass?
Lean body mass is your total body weight minus fat — comprising muscles, bones, organs, water, and connective tissue. The Boer formula estimates LBM within ±3 kg accuracy for adults in the normal-to-overweight BMI range. LBM is the figure to protect when cutting calories: if you lose weight too fast without adequate protein and resistance training, you lose muscle along with fat.
How It Works
The Boer formula (1984) estimates lean body mass from total body weight and height. It was derived from direct cadaver analysis and remains a standard clinical reference for drug dosing, anesthesia, and nutritional assessment.
Formula
// Male
LBM (kg) = 0.407 × weight_kg + 0.267 × height_cm − 19.2
// Female
LBM (kg) = 0.252 × weight_kg + 0.473 × height_cm − 48.3Where weight_kg is total body weight in kilograms and height_cm is standing height in centimeters.
Derived outputs:
Worked Example
A 35-year-old male weighing 185 lb (83.9 kg) and standing 5 ft 11 in (180.3 cm):
| Step | Calculation | Result |
|---|---|---|
| LBM (kg) | 0.407 × 83.9 + 0.267 × 180.3 − 19.2 | 66.0 kg |
| LBM (lb) | 66.0 × 2.20462 | 145.5 lb |
| Fat Mass | 83.9 − 66.0 | 17.9 kg (39.5 lb) |
| Lean % | 66.0 / 83.9 × 100 | 78.7% |
| Body Fat % | 17.9 / 83.9 × 100 | 21.3% |
For a female weighing 140 lb (63.5 kg) and standing 5 ft 5 in (165.1 cm):
| Step | Calculation | Result |
|---|---|---|
| LBM (kg) | 0.252 × 63.5 + 0.473 × 165.1 − 48.3 | 45.9 kg |
| LBM (lb) | 45.9 × 2.20462 | 101.2 lb |
| Fat Mass | 63.5 − 45.9 | 17.6 kg (38.8 lb) |
| Body Fat % | 17.6 / 63.5 × 100 | 27.7% |
LBM Reference Table — Males (5 ft 10 in / 177.8 cm)
| Total Weight | LBM (kg) | LBM (lb) | Fat Mass (kg) | Body Fat % |
|---|---|---|---|---|
| 140 lb (63.5 kg) | 49.7 kg | 109.6 lb | 13.8 kg | 21.7% |
| 160 lb (72.6 kg) | 53.4 kg | 117.7 lb | 19.2 kg | 26.4% |
| 180 lb (81.6 kg) | 57.0 kg | 125.7 lb | 24.6 kg | 30.1% |
| 200 lb (90.7 kg) | 60.7 kg | 133.8 lb | 30.0 kg | 33.1% |
| 220 lb (99.8 kg) | 64.4 kg | 141.9 lb | 35.4 kg | 35.5% |
All values computed with the Boer (1984) formula at 5 ft 10 in height.
LBM Reference Table — Females (5 ft 5 in / 165.1 cm)
| Total Weight | LBM (kg) | LBM (lb) | Fat Mass (kg) | Body Fat % |
|---|---|---|---|---|
| 110 lb (49.9 kg) | 37.2 kg | 82.0 lb | 12.7 kg | 25.4% |
| 130 lb (59.0 kg) | 39.6 kg | 87.3 lb | 19.4 kg | 32.9% |
| 150 lb (68.0 kg) | 42.1 kg | 92.8 lb | 25.9 kg | 38.1% |
| 170 lb (77.1 kg) | 44.6 kg | 98.3 lb | 32.5 kg | 42.1% |
| 190 lb (86.2 kg) | 47.1 kg | 103.8 lb | 39.1 kg | 45.4% |
All values computed with the Boer (1984) formula at 5 ft 5 in height.
Body Fat % Reference Ranges (ACE)
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Acceptable | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Limitations
Disclaimer: Los resultados son orientativos y no reemplazan la consulta médica profesional. Antes de tomar decisiones con impacto, consultá con un médico, nutricionista o profesional de la salud matriculado.
Frequently asked questions
What is lean body mass?
Lean body mass is total body weight minus fat mass. It includes skeletal muscle, bone, organs, skin, water, and connective tissue. It is sometimes called 'fat-free mass,' though technically lean body mass retains a small amount of essential fat (~2–3% in men, ~10–13% in women).
How do I calculate lean body mass?
Use the Boer formula: males → LBM (kg) = 0.407 × weight_kg + 0.267 × height_cm − 19.2; females → LBM (kg) = 0.252 × weight_kg + 0.473 × height_cm − 48.3. For example, a 180 lb (81.6 kg) male at 5 ft 10 in (177.8 cm): LBM = 0.407 × 81.6 + 0.267 × 177.8 − 19.2 ≈ 62.5 kg (137.8 lb).
Why use the Boer formula instead of others?
The Boer (1984) formula was developed from cadaver dissection data, giving it strong anatomical grounding. It performs well across a moderate range of body sizes and is widely cited in pharmacology for drug dosing. The James and Hume formulas are alternatives used in some clinical protocols.
How accurate is this estimate?
The Boer formula has a reported standard error of approximately ±3 kg for most adults within a normal BMI range. Accuracy decreases at very high or very low BMI. For precise measurement, DEXA scanning or hydrostatic weighing is recommended.
How do I use LBM to set a protein target?
Most sports nutrition guidelines recommend 1.6–2.2 g of protein per kg of lean body mass per day for individuals seeking to build or preserve muscle during resistance training. For example, 65 kg LBM × 2.0 g/kg = 130 g of protein per day.
Why does sex matter for the formula?
Men and women distribute lean mass and fat differently due to hormonal and physiological differences. Women carry proportionally more essential fat (stored in reproductive tissues), so the female equation has different coefficients to reflect a typically lower lean mass percentage at the same weight and height.
Is lean body mass the same as muscle mass?
No. Lean body mass includes all non-fat tissue: muscle, bone, water, organs, and connective tissue. Skeletal muscle typically makes up about 40–50% of LBM in healthy adults. To isolate muscle mass, you would need imaging methods like DEXA or MRI.
Can I use this for medication dosing?
This calculator provides an LBM estimate consistent with the Boer formula used in many clinical references (e.g., for renally cleared drugs, vasopressors, paralytics). However, dosing decisions must always be made or verified by a licensed healthcare provider following institutional guidelines.
What body fat % is considered healthy?
The American Council on Exercise (ACE) categorizes body fat roughly as: Essential fat: 2–5% (men), 10–13% (women); Athletes: 6–13% (men), 14–20% (women); Fitness: 14–17% (men), 21–24% (women); Acceptable: 18–24% (men), 25–31% (women); Obese: 25%+ (men), 32%+ (women). These are general guidelines, not clinical cutoffs.
Does LBM change with age?
Yes. Adults typically lose 3–8% of muscle mass per decade after age 30, a process called sarcopenia. Tracking LBM over time with a consistent method can help identify and address this loss through resistance training and adequate protein intake.
Sources & references
- Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans (1984) — American Journal of Physiology / PubMed (NIH) (1984)
- NIH Body Weight Planner — scientific basis for weight and composition estimates — National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (2026)
- CDC — Assessing Your Weight and Health Risk — Centers for Disease Control and Prevention (2025)
- American Council on Exercise — Percent Body Fat Norms — American Council on Exercise (ACE) (2024)
- Morton RW et al. — A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength (2018) — British Journal of Sports Medicine / PubMed (NIH) (2018)
Methodology & trust
Editorial
Calculadora de salud revisada por el equipo editorial de Hacé Cuentas, contrastada con Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans (1984), según nuestra política editorial y metodología.
Updates
Última revisión: June 20, 2026. Los parámetros se verifican periódicamente con las fuentes citadas.
Privacy
Calculations run 100% in your browser. We do not store or transmit your data.
Limitations
Indicative results. For critical decisions, consult a professional.
📌 How to cite this calculator
Rodríguez, M. (2026). Lean Body Mass (LBM) Calculator. Hacé Cuentas. https://hacecuentas.com/lean-body-mass-calculator
Contenido bajo licencia CC-BY 4.0 — reutilizable citando la fuente con enlace a Hacé Cuentas.