Skip to content

What Size Air Purifier Do You Need for Your Room?

Shopping for an air purifier and not sure what size you need? Here’s where I’d start, with a bedroom like ours.

By Franco N.·Updated October 22, 2026

Some stores pay me when you buy through a link here, and your price stays the same. As an Amazon Associate I earn from qualifying purchases. How this works

The short answer

For a bedroom like ours, about 9 by 20 feet, get the Coway Airmega Mighty2. It’s more than big enough for that, and it’s quiet on its lowest speed, the one you want at night.

I had to dig out a three-year-old floor plan to learn how big our bedroom is. We’re shopping for a purifier for it now, to replace our Winix.

In 2021 we bought a Levoit Core 300-P and put it in our bedroom. Maybe it was alright for our room size, but we didn’t feel like it, so it moved to our home office, which is smaller.

My wife didn’t like the filters either. She kept having to buy new ones, because they weren’t washable.

If you’re shopping for one too, think first about where it’s going. Here’s what I’d get for each kind of room.

Which purifier fits your room?

A small bedroom, a nursery or an office

If the room is smaller than ours, like a 10 by 12 bedroom, a nursery or a home office, get the Levoit Core 300. It’s the one we moved out of our bedroom.

Levoit Core 300An affordable purifier made for a small room
AeraMax 90 vs 190 vs 290Which size to get, if you’d rather have an AeraMax

A bedroom like ours

Get the Coway Mighty2. It has no ionizer, so it gives off no ozone while you sleep.

If you want an app, or a room size an independent lab has checked, get the Levoit Vital 200S instead.

Coway Airmega Mighty2One filter a year, and a dust reading right on the unit
Levoit Vital 200SQuiet on its lowest speed, and it has an app

A living room

For a living room, I’d get the Levoit Vital 200S. It’s big enough for a 15 by 20 room.

If yours is bigger, put it into the calculator below. When no single purifier is big enough, it looks for a pair.

Levoit Vital 200SOur review, and why it suits a living room

Smoke and smells

For smoke from the stove or a wildfire, you want a carbon filter, because HEPA on its own does nothing for smells or gases. I’d look at the Coway Mighty2 first, since the carbon is in its one filter, with no separate one to buy.

If you already have a Core 300, swap in Levoit’s Toxin Absorber filter, which adds carbon for smoke.

Coway Airmega Mighty2Carbon and HEPA in one filter
Levoit Core 300 filtersSwap in the Toxin Absorber filter for smoke

Dry air

If dry air is what bothers you, get a humidifier or an air washer instead of a purifier.

If you want the dust filtered too, look at the Boneco H680. It adds moisture and cleans the air in one machine. If moisture is all you need, look at an air washer like the Boneco W200.

Air washer vs humidifierWhat each one does, and which one you need
Boneco W200An air washer that adds moisture to a dry room
Boneco H680Adds moisture to a big room

Fewer filters to buy

If you’d rather buy filters less often, get the Coway Mighty2. Where the Core 300 needs a new filter every 6 to 8 months, the Mighty2 takes just one a year.

Coway filtersWhich filters each Coway Mighty takes
AeraMax and Boneco replacement filtersWhich filter to order for an AeraMax or a Boneco

What if your room is somewhere in between?

Tap the example room closest to yours. If you know how long your walls are, type them in instead.

Free tool

Air purifier size and running cost

Type in your walls, or tap a room near yours. You get the size of purifier it needs, which ones reviewed here are big enough, how often their filters need changing, and what each costs to run.

Try a room:

How fast should it clean the air?

Smoke CADR is the clean-air number on the box, in cubic feet a minute. Bigger moves more air.

    How the calculator works
    • AHAM rates purifiers to clean a room’s air 4.8 times an hour, in a room with an 8 ft ceiling. The calculator uses the equation from AHAM’s 2026 white paper with your own ceiling in place of 8 ft. That swap is ours, since AHAM’s rule assumes 8 ft. At 8 ft it matches AHAM’s room-size rule to within a point and comes in a little under the EPA’s two-thirds rule.
    • The faster setting is Harvard Healthy Buildings’ “ideal” of 6 air changes an hour.
    • Levoit’s smoke CADR figures are from AHAM’s live directory. The AeraMax 90, 190 and 290 figures are from AHAM’s October 2023 directory, because the live one no longer lists them. The two Coway figures are Coway’s own, since Coway is not in AHAM’s directory.
    • The filter times come from each purifier’s manual or product page, and where Levoit gives a range, the card shows both ends. On the AeraMax, a light turns red when a filter is due. Coway bases the Mighty’s times on 8 hours a day at top speed, and one filter set, with a HEPA filter and two odor filters, covers a year.
    • Power is each brand’s rated wattage, which is the most it can draw. On a lower speed it uses less, so treat it as the most you would pay. We have not read a wattage for the AeraMax models yet.

    Sources: AHAM white paper, AHAM directory, EPA guide to air cleaners, Harvard Healthy Buildings, and the Levoit, Coway and Fellowes manuals and product pages. Ratings, wattages and filter details read 14 September to 13 October 2026.

    The purifiers we review, by room size

    Purifier Room up to Price and seller
    Fellowes AeraMax 90 100 sq ft
    AHAM certified, 2023    		 See price at Paper Machines
    Review and sellers
    Fellowes AeraMax 190 200 sq ft
    AHAM certified, 2023    		 See price at Clary Business Machines
    Review and sellers
    Levoit Core 300 222 sq ft
    AHAM certified    		 See price at Amazon
    See price at Levoit
    Fellowes AeraMax 290 300 sq ft
    AHAM certified, 2023    		 See price at Staples, in stores only
    Review and sellers
    Coway Airmega Mighty 361 sq ft
    Coway’s own figure    		 See price at Amazon
    See price at Coway
    Coway Airmega Mighty2 372 sq ft
    Our math on Coway’s figures    		 See price at Amazon
    See price at Coway
    Levoit Vital 200S 388 sq ft
    AHAM certified    		 See price at Amazon
    See price at Levoit

    Room sizes are AHAM’s certified sizes where it has one and the brand’s own where it doesn’t, all for an 8 ft ceiling. Coway gives the Mighty2 no such figure, so its line is our arithmetic from Coway’s clean-air figure.

    The listing says it covers a huge room. Will it cover mine?

    Our own Core 300’s Amazon title says “Up to 1073 ft²”. AHAM certifies the same purifier for 222 square feet.

    The bigger number isn’t made up. It’s the room the purifier can get through once an hour. Buy by the certified size, the room it can clean almost five times an hour.

    I trust the size on the AHAM seal, because independent labs check it. You’ll find it on the box, or by searching the model in AHAM’s online directory.

    Coway has no seal, and I’d still get the Mighty2. The room size it prints for the original Mighty holds up under AHAM’s own math. The same math puts the Mighty2 at 372 square feet, more than twice the size of our bedroom.

    If a listing gives a room size with no seal and no clean-air figure behind it, treat it as a sales number.

    Every air care page

    Questions people ask

    What does CADR mean on an air purifier?

    Clean air delivery rate, how much filtered air the purifier puts out each minute, in cubic feet. There’s one number each for smoke, dust and pollen, and the room size comes from the smoke one.

    How do I work out the room size from the CADR?

    Multiply the smoke CADR by 1.55. The Core 300’s smoke CADR of 143 comes out at 222 square feet, the size AHAM certifies it for.

    How much clean air does my room need?

    Divide your square feet by 1.55 and look for a smoke CADR at least that high. A 100 square foot room needs about 65, a 200 square foot room about 130, and a 300 square foot room about 194. The calculator above does it for any room.

    Does ceiling height change what size I need?

    Yes. A taller room holds more air, so it needs a bigger purifier.

    AHAM’s room sizes assume an 8-foot ceiling. If yours is higher, put your real height into the calculator above or into Harvard’s sizing tool.

    How many air changes an hour should a purifier manage?

    I’d aim higher than the 4.8 the certified room size assumes, if you can. Harvard’s sizing tool calls 6 ideal. To get there, buy a purifier certified for a room at least a quarter bigger than yours, or pick “Faster” in the calculator above.

    Sources (14)

    Prices and stock read by hand on Oct 13, 2026.

    How these numbers get checked: How Corner Nook researches these pages.

    I sold contract-grade furniture from 2016. More about who runs it.