To make a rubber band ball you will need a lot of rubber bands, most likely a whole bag full. The more rubber bands you have, the better and bigger your rubber band ball will be. To start your rubber band ball you can tie a rubber band in a knot. Then put each rubber band in two and wrap them around the first rubber band. If you keep doing this until all of your rubber bands are gone then you will have a good rubber band ball. The size of the rubber band ball depends on the number of rubber bands that you have.