CADR Rating Explained
CADR is the single most important spec when buying an air purifier. It tells you exactly how much clean air the purifier delivers - ignore the marketing claims.
What Is CADR?
CADR (Clean Air Delivery Rate) measures the volume of filtered air delivered by an air purifier, expressed in cubic metres per hour (m³/h)or cubic feet per minute (CFM). Higher CADR = faster air cleaning.
Three Types of CADR
Smoke CADR
Particles: 0.09-1.0 μm
Cigarette smoke, cooking fumes, wildfire particles
Dust CADR
Particles: 0.5-3.0 μm
House dust, mold spores, pet dander
Pollen CADR
Particles: 5.0-11.0 μm
Pollen, large dust particles, fibers
Most manufacturers report a single CADR number, typically the average or smoke CADR. For allergy sufferers, focus on dust CADR.
CADR by Room Size (at 5 ACH)
For effective air cleaning (allergies, asthma, smoke), aim for 5-6 air changes per hour. Here's the minimum CADR you need:
| Room Type | Size | Min CADR | Recommended CADR |
|---|---|---|---|
| Small Bedroom | 10m² | 200+ | 200-300 m³/h |
| Double Bedroom | 15m² | 300+ | 300-400 m³/h |
| Living Room | 25m² | 500+ | 500-600 m³/h |
| Large Living Room | 35m² | 700+ | 700-850 m³/h |
| Open Plan Kitchen/Living | 45m² | 900+ | 850+ m³/h |
Common CADR Mistakes
Mistake: Trusting "room coverage" claims
Manufacturers calculate coverage at 1-2 ACH. For effective cleaning, you need 5-6 ACH. Their "50m² coverage" may only be 15-20m² at proper ACH.
Mistake: Ignoring the ACH factor
ACH (Air Changes per Hour) determines how often all air in your room passes through the filter. 5-6 ACH is recommended for allergy relief.
Mistake: Comparing CADR across brands
Some brands test at different speeds. Always compare CADR at max speed for fair comparison.
Mistake: Assuming bigger is always better
An oversized purifier in a small room wastes energy and money. Right-size for efficiency.
The CADR-to-Room-Size Formula
Room Size (m²) = CADR ÷ (ACH × Ceiling Height)
Example: For 5 ACH with 2.4m ceiling: Room Size = 600 CADR ÷ (5 × 2.4) = 50m²
Simple Rule: Quick rule: Divide CADR by 12 for room size at 5 ACH (assumes 2.4m ceiling)
Real Coverage vs Marketing Claims
See how "room coverage" marketing compares to actual effective coverage at 5 ACH:
| Model | CADR (m³/h) | Real Coverage (5 ACH) | Marketing Claim (1-2 ACH) |
|---|---|---|---|
| Luggable XL Ultra | 850 | 65m² | 325m² (marketing) |
| Luggable Ultra | 600 | 45m² | 230m² (marketing) |
| Brisk Box | 400 | 30m² | 150m² (marketing) |
| Dyson HP09 | 290 | 22m² | 110m² (marketing) |
| Levoit Core 400S | 400 | 30m² | 150m² (marketing) |
Notice how some products claim 3-5x more coverage than they can actually deliver at effective air change rates.
Related Guides
Calculate Your Exact CADR Needs
Enter your room dimensions and desired ACH to get a precise CADR recommendation.
ACH Calculator