Air Purifier Room Size Calculator
Multiply your room’s length by its width, then compare the result with the clean air delivery rate (CADR). AHAM’s 2/3 rule asks for a smoke CADR of at least two-thirds of the room’s square footage; ENERGY STAR’s chart uses 65 cfm per 100 sq ft. Both assume an 8-foot ceiling.
Calculate
Enter your numbers to see the result. Without JavaScript, use the official table below.
The official table
ENERGY STAR’s sizing chart for particle removal (8-foot ceiling):
| Room area (sq ft) | Minimum CADR (cfm) |
|---|---|
| 100 | 65 |
| 200 | 130 |
| 300 | 195 |
| 400 | 260 |
| 500 | 325 |
| 600 | 390 |
AHAM’s 2/3 rule: “the CADR of your air cleaner should be equal to at least two-thirds of the room’s area” (example: a 120 sq ft room needs a smoke CADR of at least 80). For wildfire smoke AHAM recommends a smoke CADR equal to the room’s square footage. With ceilings above 8 feet, AHAM says an air cleaner rated for a larger room is needed.
How the result is worked out
Area = length × width. Minimum CADR = area × the rule you choose (2/3, 0.65 or 1). The model list shows ENERGY STAR certified air purifiers whose listed smoke CADR is at least that figure, starting from the smallest qualifying CADR; it is an ordering, not a recommendation. If your ceiling is higher than 8 feet, enter a larger room area, as AHAM advises.
Full shortlists
- Air Purifiers with No Reported Ozone
- Air Purifiers with Wi-Fi
- Air Purifiers for 200 Sq Ft Rooms
- Air Purifiers for 300 Sq Ft Rooms
- Air Purifiers for 400 Sq Ft Rooms
- Air Purifiers for 500 Sq Ft Rooms
- Air Purifiers for 800 Sq Ft Rooms
- Air Purifiers for Small Rooms (Up to 150 Sq Ft)
- Air Purifiers Listed with a HEPA Filter
- Air Purifiers with an Air Quality Sensor
- Air Purifiers with a Timer
- Wi-Fi Air Purifiers with an Air Quality Sensor
- HEPA Air Purifiers with No Reported Ozone
- Low-Energy Air Purifiers (100 kWh/Year or Less)
- Energy-Efficient Air Purifiers
- ENERGY STAR Most Efficient Air Purifiers
Sources
- AHAM Verifide: Air filtration standards (the 2/3 rule)
- ENERGY STAR: Room air cleaners buying guidance (sizing chart)
Model specs: ENERGY STAR product data (data.energystar.gov, updated 2026-11-06). We compile and compare published data; we do not run our own product tests. See How We Compare.