What size air purifier do I need for my room?

Multiply the purifier's smoke CADR (cubic feet per minute) by 1.55 to get the room size in square feet at an 8 ft ceiling and 4.8 air changes an hour. A 300 sq ft room needs about 190 CFM. Use the smoke CADR from the ENERGY STAR or AHAM Verifide listing, not the room size printed on the box.

Is the Levoit Core 600S-P ENERGY STAR certified?

Yes. On 21 October 2026 the ENERGY STAR certified room air cleaner list showed it as model LAP-C601S-WUS with a smoke CADR of 391 CFM, a room size of 606 sq ft and 387 kWh a year.

Why does the box say a much bigger room than the registry?

The box figure usually assumes one air change an hour; the registry figure assumes about 4.8, which is what you need for smoke and allergens. The same Levoit Core 600S-P is quoted at 2,909 sq ft on the maker's page and 606 sq ft in the ENERGY STAR list.

Air Purifier Size by Room: ENERGY STAR Certified Picks (Oct 2026)

The rule, in one line

Smoke CADR (cubic feet per minute) × 1.55 = the room size in square feet, at an 8 ft ceiling and 4.8 air changes an hour. That is the formula AHAM uses and the one behind every room size below. Your room is 300 ft²? You need about 190 CFM. Exact numbers for ten room sizes →

ENERGY STAR certified models by room size

Every row is an entry in the ENERGY STAR certified room air cleaner list, read on 21 October 2026. Room size and CADR are the registry's own figures. Electricity is the registry's yearly kWh at $0.17 per kWh. "CFM per watt" is the registry's efficiency rating: higher is cheaper to run for the same clean air.

Sorted by the registry's room size. We name a model only where the maker's own page or manual ties the name to the registry's model number.
Room	Model	Smoke CADR	Room (ft²)	Electricity / yr	CFM per W
Up to 150 ft²	Blueair Blue Pure 411 Pure 411	98	152	64 kWh · $11	9.1
150–250 ft²	Levoit Eleva 300X LAP-C341S-WUSZ · name per Levoit's manual	161	250	145 kWh · $25	6.5
250–400 ft²	Levoit Core 400S Core 400S	231	358	237 kWh · $40	5.8
250–400 ft²	Coway AP-1523D AP-1523D · Coway lists it by model number only	255	395	219 kWh · $37	6.8
400–550 ft²	Levoit Eleva 500X LAP-C511S-WUS · most efficient in this group	301	467	194 kWh · $33	9.0
400–550 ft²	Coway Airmega 300 AP-1515H	315	488	314 kWh · $53	6.0
400–550 ft²	Blueair Blue Pure 211+ Pure 211+	348	539	350 kWh · $60	5.8
550–700 ft²	Coway Airmega 350 AP-1924A	360	558	344 kWh · $58	6.3
550–700 ft²	Coway Airmega 400 AP-2015F	376	583	366 kWh · $62	6.1
550–700 ft²	Levoit Core 600S-P LAP-C601S-WUS · our large-room pick; $299.99 at levoit.com on 21 Oct 2026	391	606	387 kWh · $66	6.0
550–700 ft²	Coway Airmega 450 AP-2524B · also 450S (AP-2524C): 443 / 687 / 399 kWh	443	687	389 kWh · $66	6.7
700 ft² and up	Coway Airmega ProX AP-3522F · most airflow per watt on this page	577	894	335 kWh · $57	10.2

Levoit's own page for the Core 600S-P lists the registry's 606 ft² next to "2,909 ft²" — the second figure is at one air change an hour. Same machine, different assumption. That is why we use the registry.

Levoit Core 600S-P on Amazon (check the current price) →

About our own picks

Levoit Core 600S-P — on the ENERGY STAR list as LAP-C601S-WUS: smoke CADR 391, room 606 ft². Our large-room pick on The Air Math.
Levoit Vital 200S-P — not on the ENERGY STAR list on 21 October 2026. Its smoke CADR of 250 (room 388 ft²) comes from the AHAM Verifide directory, which we read on 11 August 2026. Two registries, one rule; we say which one each number comes from.
Levoit Core 300S-P — withdrawn from our picks on 19 October 2026; not on the ENERGY STAR list either.

Not on the list does not mean a bad machine. It means ENERGY STAR has not certified that model's efficiency; the CADR may still be verified by AHAM. Check both.

Check any purifier yourself in two minutes

Find the model number on the box or the maker's page (for Levoit it starts with LAP-; for Coway with AP-).
Search it in the ENERGY STAR product finder or the AHAM Verifide directory.
Take the smoke CADR and multiply by 1.55. That is the room it really covers.
Room bigger than that? Size up, or run two units. A bigger box claim does not change the airflow.

Do you even need one?

Measure first. A $60 PM2.5 meter tells you whether your bedroom air is a problem before you spend $300 on a purifier. If the meter stays low, buying nothing is the right answer.

Do your own math →

Disclosure

The Levoit link is a plain link; we earn nothing if you buy. The other models on this page carry no link. Whether a model is in the table depends only on the ENERGY STAR list, not on whether we earn anything from it.