VE is the actual air flow of an engine verses the theoretical maximum. Cylinder head design, valve guides intake manifolds etc. all work to reduce efficiency by some percentage.
The easiest formula for a 4 stroke engine. CU inches X desired RPM / 3456 equals the VE at 100% for the given RPM. This number should be adjusted for the flow efficiency of a given engine ie: times 80 90 or 100 %. Most HP street vehicles are around 80% Very high performance can be around 90% All out top fuel dragsters approach 100%. It can be further adjusted for air temp, relative humidity and barometric pressure but that is probably not necessary in your case. To exceed 100% generally requires a turbo or blower. The 3456 converts cu inches to cu feet and adjusts for every other stroke in a four stroke.
Mike