What would tell you is the CFM rating for the fan, which is readily available for most electric fans and should be available in a cfm vs rpm graph for any mechanical fan worth the effort.
I've always wondered - are electric fans all rated the same way (like a static air flow at a specific voltage measured at a specific distance from the fan)? Or do the manufacturers decide the parameters that they rate their fans under? I've always felt like you kind of have to take advertised cfm numbers with a grain of salt. Unless there's some universal test method or something? Who knows.
