Lean Body Mass Calculator (Boer / Hume / James)

Lean Body Mass Calculator (Boer / Hume / James) | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Health
Input types: select, number
Output type: html
Sample coverage: 4
API ready: Yes

Overview

The Lean Body Mass Calculator estimates your lean body mass (LBM) and derived body-fat percentage using three clinical formulas—Boer, Hume, and James—side by side. By inputting your sex, age, weight, and height in either metric or imperial units, you can instantly compare these established medical equations to better understand your body composition and track muscle mass.

When to use

When tracking body composition changes during a fat loss or muscle building phase.
When calculating precise macronutrient targets or daily energy expenditure based on lean mass.
When comparing clinical formulas like Boer, Hume, and James to get a balanced estimate of fat-free mass.

How it works

1Select your sex and enter your current age.
2Input your body weight and height, choosing either metric (kg, cm) or imperial (lb, in) units.
3Adjust the decimal precision and run the calculation to view the side-by-side results of the Boer, Hume, and James formulas, along with your average lean body mass and estimated body fat percentage.

Use cases

Fitness enthusiasts calculating lean mass to set accurate protein intake goals.
Nutritionists and dietitians estimating client body composition using clinical formulas.
Athletes tracking changes in muscle mass versus fat mass over a training cycle.

Examples

1. Tracking Muscle Retention During a Cut

Strength Athlete

Background

An athlete weighing 70 kg at 175 cm wants to monitor their lean mass to ensure they are not losing muscle during a calorie deficit.

Problem

Needs to establish a baseline lean body mass using multiple clinical formulas to track body composition changes.

How to use

Selects 'Male', enters age 30, weight 70 kg, and height 175 cm, then sets the decimal precision to 1.

Sex: Male, Age: 30, Weight: 70 kg, Height: 175 cm, Precision: 1

Outcome

Calculates an average lean body mass of 58.8 kg (Boer: 59.4 kg, Hume: 58.2 kg, James: 58.8 kg) and an estimated body fat percentage of 16%.

2. Client Assessment in Imperial Units

Personal Trainer

Background

A trainer needs to estimate the lean mass of a female client who tracks her progress in pounds and inches.

Problem

Wants to quickly calculate LBM and body fat percentage without manual unit conversions.

How to use

Selects 'Female', enters age 28, weight 140 lb, and height 65 in, keeping the default decimal precision.

FAQ

What is Lean Body Mass (LBM)?

Lean Body Mass is the weight of everything in your body except fat, including muscles, bones, organs, and water.

What is the difference between the Boer, Hume, and James formulas?

These formulas use slightly different mathematical coefficients based on historical clinical studies to estimate fat-free mass from height and weight.

Which formula is the most accurate?

The Boer formula is widely used as a clinical standard, but comparing all three side-by-side provides a more reliable average estimate.

Does this calculator support imperial units?

Yes, you can input weight in pounds (lb) and height in inches (in), which are automatically converted for the calculations.

How is the body fat percentage derived?

The calculator subtracts the estimated lean body mass from your total body weight to determine fat mass, then calculates it as a percentage of your total weight.

Sex: Female, Age: 28, Weight: 140 lb, Height: 65 in, Precision: 1

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Tracking Muscle Retention During a Cut

2. Client Assessment in Imperial Units

FAQ

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