A square plane with added subdivision levels does not get you to a square grid? It will give you a perfect circle. Its the easiest way dude.

Im sure lisarichie's way would work too but wow seems really complicated?

Also never use tris in cloth it will make your lighting look like crap because the quads will bend in the middle. Doh! Unless polycount is of no matter to you then hey go for it. Everyone loves a 2 million poly skirt :)