BigJ12,

You don't!

IBO speed is a standard rating used by most bow companys to compare apples to apples, i.e. if you wanted to compare an Xtec to an Outback (on paper that is) you could check their IBO speeds.

Don't put a lot of concern/thought into IBO speed because it probably doesn't mean crap to you anyway. Not many people shoot a 30" draw and a 350 grain arrow.

Your draw weight, draw length, arrow weight, and various equipment on your bow and arrows for that matter, will effect your personal arrow speed. Take your bow to the local bow shop and ask to shoot it through a cronograph. Then you will know your bow speed.