What CADR do I need for a 1000 sq ft room?

About 640 CFM. With an 8 ft ceiling the room holds 8,000 cubic feet; AHAM's room-size rating assumes 4.8 air changes per hour, so 8,000 x 4.8 / 60 = 640 CFM.

Is one air purifier enough for 1000 square feet?

No. At 4.8 air changes per hour a 1000 sq ft room needs 640 CFM, and the largest unit we list delivers 391 CFM. That takes 2 units.

What does running it cost for a year?

Roughly $238 a year: about $73 of electricity at 12 hours a day and $0.17/kWh, plus about $165 in replacement filters.

← The Air Math

What size air purifier do you need for a 1000 ft² room?

The short answer, the arithmetic behind it, and what it costs to run for a year. No sign-up, nothing sent anywhere.

🌀 Clean-air delivery you need

640 CFM

at 8 ft ceilings and 4.8 air changes per hour

Where that number comes from

Nobody needs to take this on faith. It is one line of arithmetic:

1000 ft² × 8 ft ceiling = 8,000 ft³ of air
8,000 ft³ × 4.8 air changes per hour = 38,400 ft³ per hour
38,400 ÷ 60 minutes = 640 CFM

CADR — clean-air delivery rate — is measured in cubic feet per minute. The 4.8 air changes per hour is the figure AHAM uses when it prints a "recommended room size" on a box, and it lines up with the EPA's guidance on matching CADR to room size. If you see a much larger room size claimed for a small unit, the manufacturer has quietly used a lower air-change rate.

It depends what you're clearing

4.8 is the labelling standard, not a law of nature. What you actually need moves with what is in the air:

Air changes/hr	Situation	CADR needed
2	general background dust	267 CFM
4	busy household, pets	533 CFM
4.8	AHAM room-size standard	640 CFM
5	allergies, smoke, wildfire season	667 CFM

Same room, same ceiling — only the air-change target changes. During wildfire smoke or a bad allergy season, size up.

So which unit covers it?

No single unit on our list covers this room. The largest one we list, the Levoit Core 600S-P, delivers 391 CFM — you need 640 CFM, so it takes 2 units. Anyone selling you one purifier for 1000 ft² at this air-change rate is quietly assuming a lower one.

Levoit Core 300S-P — 141 CFM, too small — tops out around 220 ft². It is the budget pick — same HEPA filtration, app and auto mode, very quiet (down to about 22 dB), just less airflow.
Levoit Vital 200S-P — 250 CFM, too small — tops out around 391 ft². It is the middle option — more airflow, a washable pre-filter, and a longer filter interval.
Levoit Core 600S-P — 391 CFM, too small — tops out around 611 ft². It is the large-room option — the most airflow of the three, and the only one that covers open-plan spaces on its own.

Be careful with the room sizes printed on boxes. A unit advertised for this room at a lower air-change rate is not lying — it is answering a different question than the one you are asking.

See the Levoit Core 600S-P on Amazon (2 needed) →

Some links earn us a commission at no cost to you — it's how the site stays free. We only list gear that meets our published criteria — we haven't handled every unit ourselves.

Where these numbers come from

The 391 CFM figure for the Core 600S-P is confirmed as its smoke CADR in the ENERGY STAR certified-air-cleaner registry, together with a 606 ft² room size — which is what makes the "no single unit is enough" threshold on the larger pages a registry-backed figure rather than a manufacturer claim. The 141 CFM and 250 CFM figures for the two smaller units rest on Levoit's own documentation: we could not independently verify either model in the AHAM Verifide directory, so we do not call them AHAM-verified and neither should anyone else. AHAM's own room-size formula is 1.55 × smoke CADR; the arithmetic on this page — volume × 4.8 ÷ 60 at an 8 ft ceiling — works out to 1.5625 × CADR, so we are within half a percent of the industry convention, using the same conservative input. Checked 3 August 2026.

What a year of running it costs

At 12 hours a day and $0.17 per kWh, 2 units:

Electricity	$73
Replacement filters	$165
Total per year	$238

Filters are the part people forget. Over five years they usually cost more than the machine did.

Your ceiling probably isn't 8 feet

This page assumes 8 ft because most rooms are close to it, but the number moves in direct proportion — a 10 ft ceiling makes this room need 800 CFM instead of 640. The full calculator lets you set your own ceiling height, hours of use, electricity price and air-change target, and shows the same working.

Open the full calculator →

Other room sizes

← 800 ft²

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