FFMI Calculator – Fat Free Mass Index

FFMI Calculator – Fat Free Mass Index Explained

FFMI is an alternative to body mass index which accounts for a person’s muscle mass. The average man has scored about 19. And it’s been found in tests/studies that it is hard to score above 25 without the use of steroids or other banned substances.

What is FFMI?

Lots of tests have been based on BMI. But BMI’s short comings are it does not take into account muscle mass and that is where FFMI (Fat Free Mass Index) comes in.

Being heavier or lighter but the same height takes into account fat vs muscle mass. And each higher or lower depending on the person can be a positive or negative. This is why we use FFMI. The Fat Free Mass Index takes into account the amount of muscle mass someone has versus their height.

“A study of elite athletes (some admitted steroid users and some not) combined with an analysis of 20 Mr. America contest winners from the 1939-1959 pre-steroid era, determined that a fat free mass index of 25 is pretty much an upper limit for someone who does not use steroids. A fat free mass of 19 is the average for males.”

Calculate your FFMI

  • Lean Weight = Weight * (1 – (body fat % / 100)
  • FFMI = (Lean Weight / 2.2)/ ((Feet * 12.0 + Inches) * 0.0254)2
  • Adjusted FFMI = FFMI + ( 6.3 * (1.8 – (Feet * 12.0 + Inches) * 0.0254))

ffmi calculator

FFMI interpretation and norms for men (women data below)

As discussed above, the proposed studies have reached the following conclusions in regard to what the scores mean about the body condition of the subjects. These scores are now used in practice and provide useful guidelines to everyone who wants to know where they stand in terms of muscle mass:

■ 16 – 17: below average

■ 18 – 19: average

■ 20 – 21: above average

■ 22: excellent

■ 23 – 25: superior

■ 26 – 27: scores considered suspicious but still attainable naturally

■ 28 – 30: highly unlikely scores to be obtained naturally without steroid usage

Fat Free Mass Index (FFMI): Lecture by Dr. Andrew Chappell

Fat-Free Mass Index of a Reference Population

Once the FFMI has been determined, it may be useful to compare this number to a “normal” healthy population.  This comparison may help give a realistic perspective on how much fat-free mass people carry.

What does the fat-free mass index of a normal healthy population look like?  The following is data gathered by Schutz et al. (2002) and sampled from a healthy Caucasian population of over 1,000 people.

Men (FFMI kg/m2)
18-35 y/o                16.8        17.2        18.0        18.9         19.8        20.5        21.1
35-54 y/o                17.2        17.6        18.3        19.2         20.1        21.1        21.7

Women (FFMI kg/m2)
18-35 y/o                13.8        14.1        14.7        15.4         16.2        17.1        17.6
35-54 y/o                14.4        14.7        15.3        15.9         16.7        17.5        18.0

Notice that it is unusual for men in the average population to have a FFMI greater than 22 and women to have a FFMI greater than 18.

What do these numbers mean?

Gruber et al. (2000) proposed the following:

Men (FFMI)

  • 18 – slight build with low musculature
  • 20 – average musculature
  • 22 – distinctly muscular
  • >22 – not normally achieved without weight training
  • 25 – the upper limit of muscularity without pharmacological agents (e.g., anabolic steroids)

Women (FFMI)

  • 13 – low musculature
  • 15 – average musculature
  • 17 – distinctly muscular
  • 22 – not typically achieved without pharmacological agents (e.g., anabolic steroids)


1) Schutz Y, Kyle UU, Pichard C. (2002) Fat-free mass index and fat mass index percentiles in Caucasians aged 18-98 y. Int J Obes Relat Metab Disord; 26(7):953-60

2) Kouri EM, Pope HG Jr, Katz DL, Oliva P. (1995) Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clin J Sport Med; 5(4):223-8.

3) http://journals.lww.com/cjsportsmed/Abstract/1995/10000/Fat_Free_Mass_Index_in_Users_and_Nonusers_of.3.aspx


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