Weight (kg) Enter your total body weight in kilograms (e.g., 75.5)

Height (cm) Enter your height in centimeters (e.g., 175)

Body Fat Percentage (%) Enter your estimated body fat percentage (e.g., 15)

Quick Examples:

Average Male Lean Athletic

Calculate Clear

This calculator provides estimates that may vary from clinical measurements. For accurate body composition analysis, consult a healthcare professional.

How to use: Enter your weight, height, and estimated body fat percentage into the fields above. Click "Calculate" to see your estimated Fat-Free Mass Index and lean body mass.

What Is Fat-Free Mass Index

Fat-Free Mass Index, or FFMI, is a number that measures your muscle mass relative to your height. Unlike Body Mass Index (BMI), FFMI ignores body fat. This means it helps you see how much muscle you have. It is often used by fitness fans to track muscle growth and potential. A higher FFMI usually means more muscle definition.

How Fat-Free Mass Index Is Calculated

Formula

To find your FFMI, the calculator first finds your lean weight. It does this by removing the weight of your body fat from your total weight. Then, it converts your height into meters and squares that number. Finally, it divides your lean weight by your squared height. This gives a score that is standard for different heights.

Why Fat-Free Mass Index Matters

Knowing your FFMI helps you understand your body better than just weighing yourself. It shows if your weight comes from muscle or fat. This helps you set realistic fitness goals and track your progress over time.

Why Tracking Muscle Is Important for Health

Tracking muscle mass is important because losing muscle can make you weaker as you age. If you only watch your weight, you might lose muscle instead of fat. This calculator helps you see if you are keeping your muscle while staying lean. Keeping muscle helps you stay active and healthy.

FFMI vs BMI

BMI looks at total weight compared to height, but it cannot tell the difference between muscle and fat. A very muscular person might be called "overweight" by BMI, even if they are healthy. FFMI fixes this by looking only at lean mass. Use FFMI to better understand your fitness level without the confusion of body weight.