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CADR / Room Size Calculator

Enter your room size and get the minimum recommended CADR, ACH context, and matching purifiers from AHAM-verified data. Formula and assumptions are always visible — nothing hidden.

Direct Answer

Formula: CADR (CFM) = Room Volume (cu ft) × Desired ACH ÷ 60. Room volume = sq ft × ceiling height. AHAM uses 4.8 ACH for its standard room size ratings. EPA guidance suggests 4–6 ACH for allergy/asthma concerns.

Wildfire smoke: AHAM consumer guidance recommends smoke CADR ≈ room square footage (e.g., 300 sq ft → ~300 CFM smoke CADR) for wildfire events. For general use, 2/3 of room area is the AHAM minimum guidance.

Step 1 — Room Size

Room area (sq ft)

Step 2 — Room Height & Pollutant

Ceiling height (ft)

Default 8 ft — always editable

Primary pollutant

Desired ACH (optional)

EPA: 4–6 ACH for allergy/asthma. AHAM rating basis: 4.8 ACH.

Methodology & sources: CADR formula from ANSI/AHAM AC-1 standard. Room sizing basis (4.8 ACH) from AHAM consumer guidance. Wildfire smoke sizing from AHAM consumer guidance and EPA wildfire resources. ACH guidance ranges (4–6 for allergy/asthma) from EPA Indoor Air Quality resources. Product CADR figures from AHAM Verifide database (T1) or ENERGY STAR database (T1) as noted per product. All assumptions are shown explicitly — never hidden. Learn more about CADR →