FFMI Calculator (Fat-Free Mass Index)

Calculate your Fat-Free Mass Index (FFMI), a measure of lean muscle mass relative to height that helps assess your fitness level and muscle development.

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What is FFMI?

The Fat-Free Mass Index (FFMI) is a measurement that assesses the amount of muscle mass a person has relative to their height and body fat percentage. Unlike BMI, which doesn't distinguish between fat and muscle, FFMI specifically measures lean body mass.

FFMI is particularly useful for athletes, bodybuilders, and fitness enthusiasts who want to track their muscle development over time. It provides a more accurate picture of muscle mass than BMI, especially for individuals with higher levels of muscle mass.

Calculation Formulas

Here are the formulas used in the FFMI calculation process:

1. Lean Body Mass

$$Lean Body Mass = Weight imes (1 - Body Fat Percentage / 100)$$

2. Fat Mass

$$Fat Mass = Weight imes (Body Fat Percentage / 100)$$

3. Body Mass Index (BMI)

$$BMI = \frac{\text{Weight (kg)}}{\text{Height (m)}^2}$$

4. Fat-Free Mass Index (FFMI)

$$FFMI = \frac{\text{Lean Body Mass (kg)}}{\text{Height (m)}^2}$$

5. Normalized FFMI

$$Normalized FFMI = FFMI + 6 \times (1.8 - Height (m))$$

This formula normalizes FFMI to a standard height of 1.8 meters (approximately 5'11"), allowing for better comparisons between individuals of different heights.

  • Weight = your body weight in kilograms
  • Height = your height in meters
  • Body Fat Percentage = your body fat percentage
  • The 6 × (1.8 - Height) factor normalizes the result to a standard height

How to Use This Calculator

  1. Enter your weight (in kg or lb)
  2. Enter your height (in cm, m, or ft)
  3. Input your body fat percentage
  4. Click 'Calculate' to see your FFMI and other results

FFMI Score for Men

FFMIBody fatDescription
17-1810-18%Skinny man
18-2020-27%Average man
19-2125-40%Fat man
20-2110-18%Athlete / Intermediate gym user
22-236-12%Advanced gym user
24-258-20%Bodybuilder / Powerlifter / Weightlifter

FFMI Score for Women

FFMIBody fatDescription
14-1520-25%Skinny women
14-1722-35%Average women
15-1830-45%Fat women
16-1718-25%Athlete / Intermediate gym user
18-2015-22%Advanced gym user
19-2115-30%Bodybuilder / Powerlifter / Weightlifter

FFMI Interpretation

FFMI RangeClassification
Below 18Below Average
18-20Average
20-22Above Average
22-23Excellent
23-26Superior
26-28Exceptional
Above 28Extraordinary

Note: An FFMI above 25 is often considered difficult to achieve without performance-enhancing substances, though this threshold can vary based on genetics and training history.

Important Notes

This calculator provides estimates only. Individual results may vary based on body composition, measurement accuracy, and other factors.

  • FFMI is most accurate when using precise body fat measurements. Consider using methods like DEXA scans, hydrostatic weighing, or professional skinfold measurements for best results.
  • Genetics play a significant role in muscle-building potential. Your maximum natural FFMI may be higher or lower than average based on your genetic predisposition.
  • FFMI should be used as one of several metrics to track fitness progress, not as the sole indicator of health or fitness level.