Sizing from the EPA's published minimum CADR per room area, plus the two things the box will not tell you: there is no published CADR for odours, and MERV is not a room-size rating.
“To filter particles, choose a portable air cleaner that has a clean air delivery rate that is large enough for the size of the room.”
Reads the EPA table, and nothing else. No interpolation, ever.
The method
Everything on this site reduces to the same small procedure. It takes two minutes and a tape measure.
Length × width, in square feet. The published table runs in 100 sq ft steps, a room between two rows takes the larger one, because CADR is a minimum, not a target.
EPA publishes one minimum CADR per room size. Six rows, one hundred to six hundred square feet. That number is the floor your unit must clear.
Tobacco smoke represents the smallest particles tested. When two units both clear the minimum, the higher smoke CADR is the honest tie-breaker.
The whole dataset
Transcribed verbatim from the Guide to Air Cleaners in the Home (2nd edition), retrieved 2026-08-30. Assumes an 8-foot ceiling. Beyond 600 sq ft there is no stated minimum, and this site will not invent one.
Why this site exists
Most sizing advice quietly implies a rating that nobody has published. These two refusals are load-bearing: every page here keeps them, even when a product box does not.
CADR is defined for particles, smoke, dust and pollen. There is no published CADR for gases, odours or VOCs, so no minimum exists for your room size. An air cleaner advertised as removing odours or VOCs is not making a claim you can compare between brands the way you can compare a particle CADR.
How the pollutant pages handle itMERV rates a furnace or HVAC filter by how well it captures particles, not by the size of room it can serve. EPA publishes no MERV-by-room-area table, so there is no figure to give you here. What EPA does say is that filters rated MERV 13 and above must demonstrate at least 50% removal efficiency for the smallest particles tested.
What MERV actually gradesThe library
Every page states one thing, cites where the figure comes from, and refuses where no figure exists.
The published minimum CADR for each room size, and the sizing mistakes that follow from ignoring it.
Every room sized on its own floor area, because the minimums are published per room rather than per house.
Particles have a published rating. Gases and odours do not. Every pollutant page says honestly which one it is.
What each rating on the box actually measures, and the replacement questions only the manufacturer can answer.
Checklists and cost arithmetic built around the one figure that is comparable between brands.
Measure the room, pick the rating, read the published minimum, with the refusals built in.
Open the toolFrom the redirect log
Start here
Sizing · reference
The five ways people end up with a unit that cannot do the job, and the published CADR row that would have prevented each mistake.
Updated 30 Aug 2026
ReadRooms · reference
Sizing an air purifier for a bedroom is arithmetic before it is shopping. Measure the floor area, take the published minimum CADR for that area.
Updated 30 Aug 2026
ReadRooms · reference
Sizing a kitchen is the same floor-area arithmetic as any room: between the 100 and 200 sq ft rows, the published minimum is 130 cfm.
Updated 30 Aug 2026
ReadPollutants · reference
The honest answer first: wildfire smoke is a particle problem, and particle problems are the one thing air cleaners carry a published rating for.
Updated 25 Oct 2026
ReadFilters · explainer
CADR (clean air delivery rate) is how much filtered air a purifier delivers. What the three CADR ratings mean and the EPA minimum for every room size.
Updated 25 Oct 2026
ReadBuying · commercial
The unit is bought once; the filters are bought for as long as you own it. The sticker price is the cheapest part of owning an air purifier.
Updated 30 Aug 2026
ReadEvery figure carries its source on the page, above any affiliate link. If a page cannot prove it, the page does not get published, and no pin makes the claim either.
Amazon restricts price display to their own tools, so no price appears anywhere on this site, not in a title, a table, or a sentence.
One filled suggestion per screen, disclosed above the first link, routed through a logged redirect. The answer always comes before the commerce.
The sizing briefs
New sizing pages, new published figures, and honest notes when a page refuses to answer. No “deal alerts”, this site does not show prices.
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