FFMI, or Fat-Free Mass Index, is a way of estimating how much lean mass you carry relative to your height. It’s calculated by dividing your lean body mass (total weight minus fat) by your height squared. “Lean mass” includes all body tissues other than fat (muscle, bone, organs, water, and so on), but muscle mass is the primary component we can substantially modify. As a result, FFMI works as a decent indicator of muscularity.
For most people, an FFMI of 18–19 is typical before structured lifting. 20–21 suggests a lean, athletic build, while 22–23 reflects the kind of muscularity often seen in fitness models. 24–25 is considered elite. Values of 26 and above tend to be pretty rare among drug-free lifters, and values above 28 are extremely rare for drug-free lifters.
FFMI is more useful than BMI for assessing muscularity because it accounts for body fat. However, its accuracy depends on the quality of your body-fat estimate. Think of it as a benchmark for comparison and goal-setting rather than a perfect measurement.
Both men and women can use FFMI as an indicator of muscularity, but men typically score a few points higher due to greater average muscle mass.
The primary way to raise FFMI is by building more muscle. Consistent strength training, eating enough protein, managing sleep, and following a long-term plan are the keys. Beginners can make fast progress, while experienced lifters will see slower but still meaningful improvements.
Research on natural athletes suggests that values above 25 are pretty rare – especially if you’re lean – but not impossible. Only about 2.5% of male collegiate athletes achieve values above 28. Genetics, training history, and nutrition all play a role in where someone falls on this scale.
Take our free fitness quiz below to find the most effective program for you and your fitness goals
