Foam Cut to Size using various tools such as a foam cutter, electric knife, serrated knife, or even a pair of scissors. Here are some steps you can follow to cut foam to size, Measure the dimensions of the foam you need to cut and mark them on the foam with a pen or marker. Use a straight edge or ruler to connect the marks, creating a straight cutting line. Remember to take safety precautions when using cutting tools and wear protective gear such as gloves and eye protection.