Air purifier CADR calculator
Work out the clean air delivery rate your room needs.
Air purifiers are rated by CADR, the clean air delivery rate, and the figure you need follows from your room's volume and how many times an hour you want the air changed. Enter the room and this works out what to shop against.
Questions about this tool
Why size against the smoke CADR?
AHAM measures three CADR figures, and smoke uses the smallest particles, so it produces the lowest number. Sizing against the highest of the three flatters the machine; sizing against smoke means it still works for the particles that matter most.
Is the advertised room size wrong?
Not wrong, but it carries assumptions: an 8 ft ceiling and 4.8 air changes per hour. A higher ceiling, or a need for more air changes because of asthma or wildfire smoke, means the same room needs a higher rating than the box suggests.