Consider a room that measures 8' x 10' x 8', or 640 cubic feet.
I want to install a fan and vents that will exchange the air in this
room about once every 2-3 minutes, so a fan should be rated in the
range of 210 - 320 cfm.

I need some guidance in how to calculate the appropriate free area of
the vent(s) that will allow the fan to pull air from adjoining rooms
through this room.

Any suggestions? I expected to be able to find an online
"calculator' for this scenario, but no luck so far.

Thanks