Converting from SCFM to CFM is done by dividing the SCFM by the ratio of the actual pressure and atmospheric pressure multiplied by the ratio of standard room temperature and the actual temperature. This relationship is derived from the ideal gas law, which uses the absolute pressure reading and the absolute temperature scale.
CFM, or cubic feet per minute, is a measure of the volumetric flow rate of a gas through a system. It is typically stated in the specifications of the performance of fans and blowers. Using CFM as a measurement implies that the flow rate is in actual pressure and temperatures. Although this gives some measure of performance of a system, it doesn't directly correlate to mass flow rate since gas is compressible. An example is the centrifugal fan, which is a constant CFM device. As long as the centrifugal fan speed remains constant, the volumetric flow rate is constant.
However, due to differing air densities, the actual mass flowing through can be different. The standard CFM, SCFM, remedies this by correcting the CFM value to a standardized condition of temperature and pressure. Since the air density at standard conditions are the same, the SCFM becomes a mass flow rate measurement, which makes it easy to compare conditions. Care should be taken, as standard conditions vary between definitions.