I'm not sure of what your question is either, but if you look at Activity Monitor, it will tell you what it's CPU usage is. On my system, it's floating around 0.7% without me touching anything on it. If I fiddle with process sort options, it spikes up to 3.3% for a second or 2.
And remember it's the percentage of one core, not the whole processor. So the CPU usage on a 4 core system can add up to 400% if all the cores were running flat out.