FFMI Calculator (Fat-Free Mass Index)
Fat-free mass index and muscle potential. Free, private and instant.
How to use the FFMI Calculator
- Pick metric (cm, kg) or imperial (ft, in, lb) units.
- Choose sex: Male or Female.
- Enter height.
- Enter weight.
- Enter body fat %.
- Press Calculate to get an instant result with a colour scale, chart and plain-English explanation.
About the FFMI Calculator
Fat-Free Mass Index is like BMI for muscle: it measures lean mass relative to height. Because it removes fat, it is a better gauge of muscularity than BMI for people who train.
Also known as: fat-free mass index calculator, FFMI natural limit, normalized FFMI calculator, muscle mass index calculator.
Worked example
- Sex: Male
- Height: 170 cm
- Weight: 70 kg
- Body fat %: 20%
Normalized FFMI: 20.0 kg/m² (Average). With 56.0 kg of lean mass, your FFMI is 19.4 (20.0 normalized to a 1.8 m height).
- FFMI: 19.4
- Normalized FFMI: 20.0
- Lean mass: 56.0 kg
- Fat mass: 14.0 kg
Formula and cut-offs
Lean mass = weight x (1 - body fat %). FFMI = lean mass (kg) / height (m)^2. Normalized FFMI = FFMI + 6.1 x (1.8 - height in m).
Frequently asked questions
What is a good FFMI?
For men, 18-20 is average, 20-22 is above average and 22-25 is excellent. Values above about 25 are rare without performance-enhancing drugs.
How do I get my body fat percentage?
Use the Body Fat Percentage or Relative Fat Mass calculators on MediHub, or a DEXA or skinfold measurement.
What FFMI is possible without steroids?
A widely cited study of male athletes found that a normalized FFMI of about 25 was rarely exceeded without anabolic steroids. It is a guide, not a hard limit, and it depends on an accurate body fat estimate.
What is the FFMI for a man 170 cm tall, weighing 70 kg, with 20% body fat?
Normalized FFMI: 20.0 kg/m² (Average). With 56.0 kg of lean mass, your FFMI is 19.4 (20.0 normalized to a 1.8 m height). Enter your own numbers above for a personal result.
Sources and references
- World Health Organization - Obesity and overweight fact sheet
- WHO - Waist circumference and waist-hip ratio: report of a WHO expert consultation
Written and checked by the MediHub editorial team against the sources above. Read how we build and review our calculators.
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Last updated . This calculator is for education only and is not medical advice. See the medical disclaimer.