I use the length of my racket which is 27" unless you have an extended. So if my mains are 18 feet, I just do the math to convert it to tennis racket lengths. 18 times 12 gives me 216 inches. Divide that by 27 (racket length in inches) and that gives me 8 racket lengths.
It's super fast since I know the mains on my Prince Exo3 Tour are 9 racket lengths, and the crosses are 7 plus the handle. So you could just measure the short side the same way, and you should be set.
Last edited by loosegroove; 03-28-2013 at 09:10 AM.