A good way to find the correct bar width is do a few push ups and measure from pinky to pinky on the floor. This is because your hands will naturally go out to most supportive or strongest position. Buy a bar at, or just wider, than that. Buying or using a bar that is too wide is bad too--you will then lean too far forward and your hands and arms will support too much weight and get fatigued--your shoulders and low back might start hurting too. FYI, you can carefully cut down a wide bar to a narrower width with a hacksaw or a pipe cutter.