It is possible to convert the pressure being measured to CFM. Please see below equation V=1096.5√(P/ρ) Were, V=velocity P=Pressure reading (in “ w.c.) ρ=Density (if air use 0.079620621 lb/〖ft〗^3 ) With the velocity known you can multiply the velocity by the area of the duct or pipe. Doing so will give you the Flow in CFM