Best way to break down a tileset?

Hey all. I think I have a good understanding on using tilesets from many existing examples on this site. My question is how do most of you determine the x,y cords and h,w when looking at a new tileset? Is there a tool on the ipad outside of coda that would be helpful on getting the cords and pixels? I as on the ipad cause I am doing everything here.

Thanks in advance for the help.

I had written a small app that used the ipad app sprite something. I would draw tiles in there then used the tilesheet to drag and drop all my tiles. This would export via email. I’d paste it in and my class would load the tilesheet and pull the correct tiles. I would specify how many columns and rows the sheet had. It would then calc the tile coords based on the colomns/rows and image width/height. I’ll see if I can dig it up. This method only works for sheets that have all the tiles the same size.

I use paint.net on my pc, and just hover the mouse around. It gives me the pixel position.