Pour 1 quart of water and 1/4 cup of mild dish washing soap into a 2-quart bowl. Mix the two ingredients together for 2 seconds with your hand.
Remove the computer floor mat from the carpet or the floor. If you don't lift the mat to clean it, you risk missing dirt trapped on the bottom side of the mat.
Soak a cleaning cloth in your mixture and use it to rub both sides of the mat. Polycarbonate and polypropylene mats are not affected by any type of common household detergents, so don't afraid to rub them hard.
Wipe the clean mat's surface with a dry piece of cloth. Allow the mat to dry completely before placing it back on the hard surface or the carpet, as you must not allow moisture to be trapped beneath it.