Buying the right saw to fit your cutting needs really isn't that hard if you have any slight bit of experience with a chainsaw, but if your new to the game you probably have no clue where to start. Determining the right size for what you are typically going to be cutting is a big deal. You don't want to go too small and not have enough saw to get the job done but you also don't want to go too big and muscle around more saw than you need. When looking at chainsaws the size and guide bar length directly determines the type of jobs you can do with that particular saw. So basically, the chainsaw size will determine the largest object it can cut in a single pass.