Fat-free mass index (FFMI) is a measurement that scales fat-free mass to height, often used as a general metric of muscularity.
Much of the early FFMI research focused on males, but Harty et al recently evaluated FFMI in a variety of female collegiate athletes. Of the 372 athletes, the 97.5th percentile, which could be used as a general “upper limit” for most female athletes, was 23.9. However, values as high as 27.2 were observed! These results are fairly consistent with another recent paper by Blue et al (2019), which documented several female athletes in the low-20s, and maximal observed values above 25.
In the past, it was commonly believed that drug-free males were extremely unlikely to surpass an FFMI of 25. Of course, it certainly takes some pretty elite genetics to be absolutely shredded (5-6% bodyfat) with a value of 25 or above. However, recent studies have suggested that values in the high 20s are be attainable for males within generally “athletic” body fat ranges (Trexler et al 2017, Currier et al 2019), with values above 30 observed in individuals with relatively higher body fat levels, and the current data suggest that some genetically gifted drug-free females may be able to aim for 25 and beyond, depending on their level of leanness.
The bottom line: Most female college athletes in strength-related sports had FFMI values around 20-22, but values up to (and beyond) 27 are possible.