# How do you compute invoice charges?

Render job charges are just a touch complex, but follow simple principles.  The equation used to calculate the cost of rendering a frame from a scene file is:

Time x CPUGhzhr x Rate(Power)

Time is simply the wallclock render time to complete the frame, to the nearest second.  CPUGhzhr is the compute capacity of the node that is rendering the frame.  We have an article explaining Gighertz hours, but the summary version here is that Ghzhrs is the number of CPU cores multiplied by their clockspeed.  Rate is the cost per Ghzhr you have chosen for the job when the frame begins rendering.  The rate corresponds directly with Power level, we simply use Power level as an easier-to-understand number.  Hence, rendering a single frame that takes one hour to complete on a 4 core CPU running at 3Ghz when the job had a Power level of .8 (\$0.005/Ghzhr) selected when the frame began, yields an equation that looks like this:

1hr × 12Ghzhr × \$0.005/Ghzhr = \$0.06

Another example is a frame that renders in 2.37 hours on a node with 16 CPU cores that run at 3.5Ghz with a job Power level of 2.5 (\$0.015/Ghzhr):

2.37hrs × 56Ghzhr × \$0.015/Ghzhr = \$1.99

As you can see, the invoice charges generated are simply measurements of how much compute time the frame(s) of your job consumed, multiplied by the rate you selected to pay.