This FFMI Calculator is the perfect app for bodybuilders and fitness enthusiasts because it can estimate the lean body mass, the FFMI and the adjusted FFMI. The three formulas involved can be found below:

Lean = Weight in kg x (1.0 - (Body fat %/ 100.0))

FFMI = (Lean / 2.2) / ((Height in ft x 12.0 + in) x 0.0254)2 x 2.20462

Adjusted FFMI = FFMI + (6.1 x (1.8 - ((Height in ft x 12.0 + in) x 0.0254)))

The FFMI in an index that accounts for the amount of muscle mass one person has, correlated to their weight and height. It helps track fat loss progress along with muscle building processes.

The following table introduces the FFMI scores and their interpretation in terms of muscle mass:
FFMI score Muscle mass interpretation
16 - 17 Below average
18 - 19 Average
20 - 21 Above average
22 Excellent
23 -25 Superior
26 - 27 Suspicion of steroid use*
28 - 30 Steroid usage likely**

* FFMI values of 26-27 indicate a suspicion of steroid usage but can still be attainable naturally.

** FFMI values of 28 – 30 are highly unlikely to be obtained naturally.

There are other types of body weight indices, such as the Body Mass Index (BMI) but compared to those, the FFMI is more specific.

For example, it addresses one of the main criticisms of the BMI, the fact that two subjects of same weight and height, will have the same BMI although different fat/ muscle amounts.