Air Volume Usage

In a static condition, without flow, the volume of air is expressed in Normal m3 (cubic meters). That is the water volume of the tank times the pressure. You can express that also in liters when it is a small system (one liter equals 1 dm3.

To know how much you use approximately can be derived over a time measurement.

When you close down your supply, you can time how long your air in the tank lasts, under condition that you work at a lower pressure as is in the tank. (e.g. with pressure regulator fitted output)

The pressure drop in the tank, times the volume/over the time is your flow.

You can also check how much your compressor produces and see how much you use of it.

Without flow meters or calibrated venturies, and pressure drop measurements it is not possible to calculate your flow with the parameters you provide.

It is easier to measure the run hours of the compressor over time, and multiply it by the compressor's throughput rating at the system pressure, which can be found in the User Manual.