Air Purifier Sizing Calculator | CADR & CFM by Room Size (ACH)
💨 Air Purifier Sizing Tool
Formula: CADR (smoke) = Room Area ÷ 1.5 | CADR (dust) = Room Area × 1
Why Proper Air Purifier Sizing Matters
An undersized air purifier won’t clean the air effectively, leaving allergens and pollutants behind. An oversized unit wastes energy and money. Our Air Purifier Sizing Tool uses industry-standard CADR (Clean Air Delivery Rate) and ACH (Air Changes per Hour) formulas to recommend the right capacity for your room.
Key Calculations
- CADR (Smoke): Room Area ÷ 1.5 – minimum for effective particle removal.
- CADR (Dust/Pollen): Room Area × 1 – recommended for allergy sufferers.
- Required CFM: (Room Volume × Desired ACH) ÷ 60 – based on ASHRAE 62.2.
Frequently Asked Questions (FAQ)
What is CADR?
CADR (Clean Air Delivery Rate) measures how many cubic feet of clean air an air purifier delivers per minute. Higher CADR means faster cleaning. The AHAM standard rates CADR for smoke, dust, and pollen.
How many air changes per hour (ACH) do I need?
For general residential use, 4-6 ACH is sufficient. Allergy or asthma sufferers may need 6-8 ACH. Commercial spaces or high-pollution areas often require 8-12 ACH.
Can I use this tool for HEPA purifiers?
Yes. HEPA purifiers are rated by CADR. Match the recommended CADR (smoke) to the purifier’s smoke CADR rating for best results.
What if my room has high ceilings?
Our tool includes ceiling height, so the required CFM adjusts automatically. Taller rooms need more powerful units.
Should I buy one large purifier or multiple smaller ones?
For open floor plans, one large purifier often works. For multiple rooms or closed spaces, multiple smaller units are more effective.
Disclaimer: This tool provides estimates based on AHAM and ASHRAE guidelines. For specific medical or critical environments, consult an HVAC professional.
