CPU percentage refers to the processor's capacity that is currently in use when some tasks are going on. For different processors, this percentage may vary, depending upon their strength. Generally, when the CPU is inert or nothing, in particular, is going on, this percentage is around 2 to 4 %. During gaming, it raises to 40%. But if the game is way too intense or a very demanding task is going on, this percentage can reach its fullest.