This air purifier size guide explains CADR and shows how to pick the right size for a 1BHK, 2BHK or 3BHK home. Many buyers choose by price or looks, then find the purifier too weak for the room. A small unit in a big hall barely moves the air. Size decides how well it works. Here is a simple way to get it right.
What is CADR?
CADR stands for Clean Air Delivery Rate. It measures how much filtered air a purifier delivers each minute. A higher number means faster cleaning. The test body AHAM rates purifiers for smoke, dust and pollen. Smoke is the toughest test, since smoke particles are very small.
Units can confuse you. US brands list CADR in cubic feet per minute (CFM). Many Indian brands list it in cubic metres per hour (m³/h). To convert, multiply CFM by 1.7. To go the other way, divide m³/h by 1.7.
The simple formula for your air purifier size guide
Follow AHAM’s two-thirds rule. First, measure the room’s length and width in feet. Next, multiply them to get the area. Then multiply the area by two-thirds. The result is the minimum smoke CADR in CFM.
For example, a 12 ft by 10 ft bedroom has 120 sq ft. Two-thirds of 120 is 80 CFM. That equals about 136 m³/h.
This rule assumes an 8 ft ceiling. Many Indian flats have taller ceilings, so size up. AHAM also advises a smoke CADR close to the room’s area for wildfire smoke. Winter smog in Noida can justify the same extra margin.
Room size and CADR at a glance
These figures use the two-thirds rule and an 8 ft ceiling.
|
Room |
Area |
Minimum smoke CADR (CFM) |
In m³/h |
|
Small bedroom |
120 sq ft |
80 |
136 |
|
Master bedroom |
150 sq ft |
100 |
170 |
|
Living room |
200 sq ft |
133 |
227 |
|
Large hall |
300 sq ft |
200 |
340 |
|
Open living and dining area |
500 sq ft |
333 |
567 |
Air purifier size for 1BHK, 2BHK and 3BHK homes
Room sizes vary, so measure your own. The advice below uses typical layouts.
1BHK
A 1BHK has one bedroom and a small hall. One purifier in the bedroom covers your sleeping hours. A 120 sq ft bedroom needs at least 136 m³/h. If you spend the day in the hall, size the unit for the hall instead.
2BHK
A 2BHK adds a second bedroom. One purifier per main room works best. A single strong unit can serve the hall and the nearest bedroom if the door stays open. In that case, add the two areas together before you check the CADR.
3BHK
A 3BHK has more rooms and a bigger hall. Use one larger unit for the living and dining area, and another for the master bedroom. A third unit helps if children sleep in a separate room. Open-plan halls often need a model from our rooms under 500 sq ft page. Smaller rooms fit the rooms under 300 sq ft range.
What else changes the size you need
Ceiling height matters most. A 10 ft ceiling holds 25 percent more air than an 8 ft one, so the same purifier works harder. Open doors matter too. A purifier in a room with open doors cleans a larger space than you measured.
Pollution level also counts. Heavy smoke days push any purifier hard. Therefore, a higher CADR gives you breathing room. Leave some space around the unit so air flows freely. Keep doors closed while it runs.
Common sizing mistakes
Coverage claims on boxes mislead many buyers. Some brands quote a large area but base it on a long cleaning time. One unit may clean a small room in minutes or a large room in an hour. So check the CADR, not just the coverage line.
Others forget ceiling height. A few expect one purifier to serve a whole flat. Doors, walls and distance block airflow, so one unit rarely does. Good use of this air purifier size guide means matching each main room to its own CADR.
Where to buy in Noida
Browse our air purifier collection to compare models by room size. You can also visit our stores in Sector 18, Sector 9 or Greater Noida. Use the store locator to find the nearest one. Bring your room measurements, and our team can help you match the CADR.
Keep this air purifier size guide handy when you shop. A few minutes with a measuring tape saves you from buying the wrong size.
