Enter your room's length and width. You get the minimum CADR to look for on the box.
Air purifier size calculator
Room size.
Minimum CADR
0
Room area0
For wildfire smoke (smoke CADR)0
AHAM rule of thumb: CADR at least two-thirds of room area; for wildfire smoke, a smoke CADR equal to the area. For ceilings above 8 ft we scale the area up by height / 8 so you choose a unit rated for a larger room.
How it works
AHAM's rule of thumb: CADR should be at least two-thirds of the room area. For wildfire smoke, AHAM recommends a smoke CADR equal to the room area. Rooms with ceilings over 8 feet need a unit rated for a larger room, so the calculator scales up for higher ceilings.
Source: AHAM Verifide, "Air Filtration Standards" (last modified Nov 11, 2025).