However, a general guideline can be found below if you do not have the room's exact dimensions at this time: Under 200 square feet: 2,000 to 3,000 CFM. 200 to 300 square feet: 3,000 to 4,000 CFM (typically a standard bedroom or kitchen) 300 to 450 square feet: 4,000 to 6,000 CFM (usually a master bedroom or living room ...