How much air your blasting nozzle uses, so you can tell whether your compressor can keep up. Nozzles wear bigger with use, so it also shows the demand once yours is worn.
Compressors are rated at a stated pressure. Compare these numbers with your compressor's cfm at your blasting pressure, and remember that small tank compressors can't run continuously at full output.
Air flow through an orifice rises with its area (the square of its diameter) and with the absolute pressure behind it. This calculator scales from a widely published reference point: a 1/4 in (#4) nozzle at 100 psi uses about 81 cfm. Published charts differ a little between manufacturers, so treat results as estimates.
Blasting is continuous, so a compressor needs to deliver this much air steadily, not just in short bursts from the tank.