Here's a funny one for you all... I've found this from a research article made by some Harvard Medical School professors
Can be interesting for all the newbies in here wanting to get lean and for the lean ones with or without the use of AAS to see where your're at...

How to calculate FFMI (fat free mass index):
FFMI = (W x (100 – BF)/100)/H*2+6,1 x (1,8 – H)

H= xx inches x 0.254 = x.xx meters
H*2= H x H
W= xxx pounds x 0.454 = xxx kg
BF = Body Fat

FFMI values:
20 = average
22 = visibly muscular
25 = Approximate maximum attainable by a lean individual without using drugs