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Hndy Tools

Lean Body Mass Calculator

Estimate your fat-free mass using three proven medical formulas

Health
Fitness
Body Composition

Your Measurements

About This Tool

The Lean Body Mass Calculator estimates your fat-free mass — the weight of everything in your body except fat, including muscle, bones, organs, skin, and water. It uses three well-established medical formulas: Boer (1984), James (1976), and Hume (1966).

Each formula takes your weight, height, and sex as inputs and returns a slightly different estimate. This tool shows all three results side-by-side so you can compare and use the average for a more reliable value.

For a more comprehensive body composition analysis, try our Body Fat Percentage Calculator which uses the U.S. Navy method, or our Waist-to-Hip Ratio Calculator to assess body fat distribution and health risk.

All processing happens entirely in your browser — no data is sent to any server. Your calculation history is stored locally and can be cleared at any time.

Frequently Asked Questions (FAQ)

What is lean body mass (LBM)?
Lean body mass is your total body weight minus your fat mass. It includes muscle, bones, organs, skin, and water. Knowing your LBM helps you set realistic fitness goals, track muscle gain or loss, and optimize your nutrition plan.
Which formula is most accurate for lean body mass?
The Boer formula (1984) is generally considered the most accurate for most adults. However, all three formulas — Boer, James, and Hume — are estimation methods. For the most accurate results, consider comparing with our Body Fat Percentage Calculator which uses the U.S. Navy method.
How is lean body mass different from muscle mass?
Lean body mass includes everything except fat: muscle, bone, organs, water, and connective tissue. Muscle mass is only the weight of your skeletal muscles. LBM is always higher than pure muscle mass because it includes non-fat, non-muscle tissues.
Is my data safe when using this calculator?
Yes. All calculations happen entirely in your browser. No personal data is sent to any server. Your calculation history is stored locally on your device and can be cleared at any time.
How can I increase my lean body mass?
To increase LBM, focus on resistance training, adequate protein intake (1.6–2.2 g/kg/day), progressive overload, and sufficient recovery. Track your progress with this calculator alongside our Daily Calorie Needs Calculator to dial in your nutrition.
What is a healthy lean body mass percentage?
For men, a healthy lean body mass percentage is typically 75–85% of total body weight. For women, it's around 68–78%. Athletes may have even higher percentages. Use our Ideal Body Weight Calculator to compare with medical formulas.

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