Air Purifier Room Size Calculator (CADR)
Room size and how bad your air gets - to the CADR number that actually matters, ignoring marketing claims.
Your room and your air
How bad does it get?
What you need
200 m³/hr
Minimum CADR
Compact
Purifier class
5x
Air changes per hour
💡 Ignore marketing coverage claims - match CADR to the room. For this room you need at least 200 m³/hr; anything lower will run flat-out and still lag on bad days. True HEPA (H13) only, and check the replacement filter price first.
Assumes 9 ft ceilings. Severe zones use 5 air changes/hour. Bedrooms benefit most - prioritise where you sleep.
Frequently asked questions
What is CADR?
Clean Air Delivery Rate - cubic metres of purified air per hour. It is the one spec that determines whether a purifier can keep up with your room.
HEPA or ionizer?
True HEPA (H13) only. Ionizers and 'plasma' modes can produce ozone and clean far less - treat them as gimmicks.