Lean Body Mass Calculator
Estimate lean body mass from body weight and an entered body-fat percentage. The remaining estimated weight is reported as fat mass for a simple body-composition breakdown.
How to use this calculator
- Enter body weight in kilograms and a body-fat percentage between 0 and 75.
- Check the labels and units before applying the result to a real task.
- Change one input at a time when comparing scenarios.
Formula and method
Fat mass = total mass × body-fat fraction; lean mass = total mass − fat mass
- Fat mass = total mass × body-fat fraction; lean mass = total mass − fat mass
- The result inherits the error of the body-fat estimate and does not differentiate muscle, bone, water or organs. It is not a medical assessment.
Worked examples
Worked example
A body weight of 80 kg and estimated body fat of 25%.
Estimated fat mass is 20 kg and estimated lean body mass is 60 kg.
Estimated fat mass is 20 kg and estimated lean body mass is 60 kg.
Understanding the result
Estimate lean body mass from body weight and an entered body-fat percentage. The remaining estimated weight is reported as fat mass for a simple body-composition breakdown.
The result inherits the error of the body-fat estimate and does not differentiate muscle, bone, water or organs. It is not a medical assessment.
Important notes
The result inherits the error of the body-fat estimate and does not differentiate muscle, bone, water or organs. It is not a medical assessment.
Displayed values are rounded for readability; retain appropriate precision when continuing a calculation.
Frequently asked questions
Does lean body mass mean muscle mass?
No. Lean mass includes non-fat components such as muscle, bone, water and organs; it should not be read as a direct measurement of muscle.
How accurate is the estimate?
Its accuracy depends mainly on the body-fat percentage supplied. Measurement methods vary and can have meaningful uncertainty.
Can I compare results over time?
Yes, cautiously, when the same measurement method and conditions are used. Small changes may reflect measurement noise rather than genuine change.
Affiliate recommendations
Tools related to Lean Body Mass Calculator
These tools are selected for the calculator topic. The Calc Studio may earn a commission from purchases made through affiliate links.
- Transformation Academy courses Visit partner ↗
Online courses for personal development, business, coaching, wellness, fitness, and professional growth.
- Nutrinixy AI calorie tracker Visit partner ↗
AI-powered calorie and nutrition tracking for calories, macros, weight, water, and personalized nutrition guidance.
See the Affiliate Disclosure for details.
Related calculators
- Body Fat Calculator — Estimate your body fat percentage using the US Navy method.
- Body Surface Area Calculator — Estimate body surface area using the Mosteller equation from height and weight.
- BMI Calculator — Calculate your Body Mass Index (BMI) and see which weight category you fall into.
- Heart Rate Training Zones Calculator — Estimate heart-rate training zones from age and resting heart rate using an age-based maximum and heart-rate reserve.
- Ideal Weight Calculator — Find your ideal body weight based on height, gender, and frame size.
- Macro Calculator — Calculate your protein, carbohydrate, and fat targets based on your goals.
Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
- How to Calculate Salary from an Hourly Rate — Convert hourly pay into weekly, monthly, and annual estimates and understand the assumptions behind the result.
- How to Calculate Percentage Change — Learn the percentage change formula, how to calculate increases and decreases, and why the original value matters.
- Body Mass Index (BMI) — Understand BMI, its formula, and why BMI is a screening measure rather than a complete measure of health.
This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.