Air purifier CADR and room size: how to size one correctly in India
People search this as “which air purifier CADR for my room size” · updated 2026-08
Short answer
Multiply your room area in square feet by roughly 1.6 to get the minimum CADR in m³/h for clean air in Delhi-grade pollution. A 150 sq ft bedroom needs around 240 m³/h CADR; a 300 sq ft living room needs 480+ m³/h. Insist on a true HEPA H13 filter and at least 4-5 air changes per hour (ACH).
- CADR is the single most important spec — filter branding is secondary.
- "HEPA-type" is not HEPA. Look for H13 or H14 grade.
- Filter replacement cost of ₹2,000-5,000 a year is normal; budget for it.
CADR by room
| Room | Area | Minimum CADR |
|---|---|---|
| Small bedroom | 100 sq ft | 160 m³/h |
| Master bedroom | 150-180 sq ft | 240-290 m³/h |
| Living room | 300 sq ft | 480 m³/h |
| Open kitchen + living | 450+ sq ft | 700+ m³/h or two units |
What else to check
- Activated carbon weight for odours and VOCs — a thin carbon mesh does almost nothing.
- Noise at max speed: above 55 dB is too loud to sleep beside.
- Real-time PM2.5 display rather than just a coloured light.
- Power draw in watts if it runs 8+ hours a night in winter.
Common follow-up questions
Do I need an ioniser or ozone feature?
No. Ozone-generating features can irritate the lungs. Filtration (HEPA + carbon) is what removes PM2.5.
Should I keep windows open with a purifier running?
No. Purifiers only work in a closed room; otherwise you are filtering the outdoors.