Measure the size of the rug (width and length) by rolling it out on a flat, hard surface. Don't include tassels or fringe when measuring the rug.
Subtract 2 inches from each direction measured to obtain the pad size. For example, a 60 inch by 48 inch rug requires a rug pad 58 inches by 46 inches.
Choose a rug pad that is appropriate for the type of floor the area rug will be used on. Hard surfaces like wood or ceramic tile require a non-slip pad. Placing an area rug over carpet requires a felt pad to prevent the rug from bunching up.
Purchase the pad and roll it out on a hard surface. Cut it to the necessary size using sharp scissors or a utility knife. A perfect cut is not necessary because the pad is hidden under the area rug.
Place the pad on the floor and center the rug over it.