Tool
Air purifier room-size calculator
AHAM, which runs the Verifide CADR program, suggests a smoke CADR of at least two-thirds of the room’s floor area for 8 ft ceilings. This calculator applies exactly that rule, scaled for taller ceilings. It does no guessing beyond it.
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Levoit Core 300-P
AHAM smoke CADR 143 CFM (manufacturer-published).
Check price on Amazon: Levoit Core 300-P
Levoit Core 400S-P
AHAM smoke CADR 231 CFM (manufacturer-published).
Check price on Amazon: Levoit Core 400S-PCoway AP-1512HH Mighty
AHAM smoke CADR 233 CFM (manufacturer-published).
Check price on Amazon: Coway AP-1512HH MightyHow the number is worked out
Required smoke CADR = floor area (ft²) × 2/3 × (ceiling height ÷ 8), rounded up. Example: a 12 × 15 ft room with an 8 ft ceiling is 180 ft², so it needs a smoke CADR of at least 120 CFM. Source: AHAM Verifide, “Follow AHAM’s 2/3 Rule”.
What it does not tell you
- CADR measures particles (smoke, dust, pollen), not gases or odors.
- It assumes the purifier runs on its highest speed. Most people sleep on a lower one, so a margin helps.
- Open-plan spaces count as one room. Measure the whole connected area.
- It is not medical advice. If you have asthma or another condition, ask your clinician.