Estimate Fat-Free Mass Index from height, weight, and body-fat percentage. See fat-free mass, standard FFMI, and height-normalized FFMI in metric or US units.
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Normalized FFMI adjusts the standard FFMI to a reference height of 1.80 m. Interpretation varies with sex, age, training history, and the accuracy of the body-fat estimate.
What is FFMI?
Fat-Free Mass Index compares fat-free mass with height. It is similar in structure to BMI, but it uses estimated lean mass instead of total body weight. Fat-free mass includes muscle, bone, organs, water, and other non-fat tissue.
FFMI formulas
Fat-free mass equals body weight multiplied by one minus body-fat percentage. Standard FFMI equals fat-free mass in kilograms divided by height in metres squared. Normalized FFMI equals FFMI plus 6.1 multiplied by 1.8 minus height in metres.
How accurate is the result?
The result is only as accurate as the body-fat percentage entered. Consumer scales, skinfold measurements, circumference formulas, and scans can produce different estimates.
Is a higher FFMI always better?
No. FFMI is descriptive, not a health score. Performance, mobility, medical history, nutrition, and overall well-being matter more than maximizing a single number.
Can I use FFMI to track progress?
Yes, but use the same body-fat measurement method and similar conditions each time. Trends are generally more useful than one isolated result.