Select area rugs for the high traffic areas of your home and areas where you spend time watching television, playing music or exercising. Choose large enough rugs so that they will cover the majority of the area where you walk or spend time. For instance, choose rugs that leave no more than 8 to 10 inches of floor space around them once placed on the floor or in a hallway
Measure the length and width of each rug with a tape measure and record the measurements.
Roll out the 3/8-inch-thick carpet pad in a large, level clean area and measure the required amounts of carpet pad with the tape measure. Mark the measurements with a pencil so you will have a cutting guide.
Lay a straight-edge down against the pencil marks and cut the carpet padding with a utility knife. Move the straight edge as you cut in order to cut the carpet padding evenly.
Place the carpet padding on the desired area of the floor and put the correctly sized area rug on top of the padding so that the padding doesn't show.