Free room-size calculator

How much air purifier do you actually need?

Enter the room you want to keep clean. We use the AHAM 2/3 sizing rule as a practical starting point and show the math—no email needed.

Look for a smoke CADR of at least 134 CFM for a 200 sq ft room with an 8 ft ceiling

The calculation

For a standard 8-foot ceiling, needed smoke CADR is approximately room area × 2/3. For taller ceilings, this calculator scales that result by ceiling height. The result is roughly five air changes per hour.

This is an educational sizing estimate, not a guarantee of indoor air quality or a medical recommendation. Actual performance depends on airflow, filter condition, building leakage, placement, and fan speed.