Why does every room size work out to 0.65 cfm per square foot?

EPA publishes a minimum CADR of 65 cfm for 100 square feet, 130 for 200, 195 for 300, 260 for 400, 325 for 500 and 390 for 600. Each row is the same rate, 0.65 cfm per square foot, so doubling the room doubles the published minimum. The table is one rule applied at six sizes, which is exactly why guessing a seventh row is not invention but arithmetic other sites pretend is a source.

Does this comparison cover rooms larger than 600 square feet?

No. The published table stops at 600 square feet and this comparison stops with it. For a larger space, EPA guidance treats the largest published figure as a floor for part of the area rather than a whole-room answer; this site refuses to extrapolate a minimum nobody published.

If two rows differ only in scale, why does room size matter at all?

Because the machine has to clear the whole minimum. A 600-square-foot row asks for 390 cfm, six times the 100-square-foot row, and that changes the fan, the top-speed noise and the filter cost. The proportion stays constant; the shopping decision does not.

The comparison

Six published rows, compared without embellishment

Name: EPA minimum CADR by room area
Creator: U.S. Environmental Protection Agency
License: https://www.epa.gov/indoor-air-quality-iaq/guide-air-cleaners-home

Most comparison tables on the web invent a seventh column. This one shows the six rows EPA actually publishes, and what changes between them, in exact proportion, with nothing filled in.

Put two published rows side by side

The whole EPA table, compared honestly, no interpolation between rows.

Pick the rows to compare (tap to add or remove)

200 sq ft

130

cfm minimum

Full page

400 sq ft

260

cfm minimum

Full page

What the side-by-side shows: every row works out to the same rate, 0.65 cfm per square foot. Double the room and the published minimum doubles with it. The table is one rule written six times, not six judgements.

Scale arithmetic between any two rows

Row A

Row B

Room

×3

Minimum CADR

+260 cfm

B over A

×3

From 200 sq ft to 600 sq ft the published minimum moves from 130 to 390 cfm, 260 cfm more, in exact proportion to the floor area. What the ratio does not capture: bigger rooms usually mean bigger machines, and bigger machines mean a louder top speed and a costlier filter. Read the noise section of the full page before you commit.

The complete comparison, all six rows

EPA published room sizes and minimum CADR, compared
Room area	Minimum CADR	Rate	What it fits
100 sq ft ≈ 9.3 m²	65 cfm	0.65 / sq ft	A bedroom, nursery or home office. The smallest published room, and the row most boxes quietly fail.
200 sq ft ≈ 18.6 m²	130 cfm	0.65 / sq ft	A large bedroom or small living room. Double the smallest row, twice the machine.
300 sq ft ≈ 27.9 m²	195 cfm	0.65 / sq ft	An open kitchen-diner or a big lounge. Mid-table, where "covers 300 sq ft" claims start to wobble.
400 sq ft ≈ 37.2 m²	260 cfm	0.65 / sq ft	A large open-plan living space. Check the tobacco-smoke CADR before anything else here.
500 sq ft ≈ 46.5 m²	325 cfm	0.65 / sq ft	A whole floor of a small flat. Few units clear this minimum honestly.
600 sq ft ≈ 55.7 m²	390 cfm	0.65 / sq ft	The last published row. Beyond it, nobody publishes a minimum, and this site will not invent one.

Source: U.S. Environmental Protection Agency, Guide to Air Cleaners in the Home (2nd edition) (retrieved 2026-08-30). Assumes an 8-foot ceiling. Past 600 sq ft nothing is published, treat 390 cfm as a floor for part of the space, not a whole-room answer.

What a side-by-side comparison is actually for

It fixes a floor, not a pick

Comparing rows tells you the minimum your room clears. Which unit clears it, and how quietly, is the next decision, made from the smoke CADR and the noise section of the full page.

It exposes the scale step

Moving up two rows doubles the minimum. That is the moment the machine gets bigger, the top speed gets louder and the filter gets costlier, the arithmetic makes the trade visible before you buy.

It keeps the refusals intact

There is no seventh row to show, and no CADR column for odours. A comparison that rendered either would be decoration around a guess.

One refusal this comparison keeps

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 it

Next steps

Size one room exactlyThe calculator reads the same table for a single area Why CADR beats “coverage area”The marketing figure is not the published one

Source: U.S. Environmental Protection Agency, Guide to Air Cleaners in the Home (2nd edition) (retrieved 2026-08-30). The published figures assume an 8-foot ceiling, if yours is higher, EPA advises choosing a higher CADR than the table shows.