What CADR do I need for a 350 sq ft room?

About 224 CFM. With an 8 ft ceiling the room holds 2,800 cubic feet; AHAM's room-size rating assumes 4.8 air changes per hour, so 2,800 x 4.8 / 60 = 224 CFM.

Is one air purifier enough for 350 square feet?

Yes — one Levoit Vital 200S-P at 250 CFM covers 350 sq ft at 4.8 air changes per hour.

What does running it cost for a year?

Roughly $91 a year: about $37 of electricity at 12 hours a day and $0.17/kWh, plus about $53 in replacement filters.

← The Air Math

What size air purifier do you need for a 350 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

224 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:

350 ft² × 8 ft ceiling = 2,800 ft³ of air
2,800 ft³ × 4.8 air changes per hour = 13,440 ft³ per hour
13,440 ÷ 60 minutes = 224 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	93 CFM
4	busy household, pets	187 CFM
4.8	AHAM room-size standard	224 CFM
5	allergies, smoke, wildfire season	233 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?

One Levoit Vital 200S-P covers it. Rated CADR 250 CFM, against the 224 CFM this room needs.

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, covers it. It is the middle option — more airflow, a washable pre-filter, and a longer filter interval.
Levoit Core 600S-P — 391 CFM, covers it. It is the large-room option — the most airflow of the three, and the only one that covers open-plan spaces on its own.

See the Levoit Vital 200S-P on Amazon →

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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, one unit:

Electricity	$37
Replacement filters	$53
Total per year	$91

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 280 CFM instead of 224. 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 →

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