Coway (brand store)gray $749
Shippingabout 3–7 days
Returns–
Coway Airmega 400S
Rank 9 of 9 robots for open-plan spaces in our ranking, tested by .in our ranking, tested by
Score 5.0 out of 10
Lab tests, 60% of the score: no lab has tested it.
Owners’ ratings, 25%: none yet at the stores that ship to the United States, so this part is left out and the others count for more.
Features, 15%: 5.0, 32 of the 64 points for the facts the maker states.
Price does not count, so a discount never lifts a model. Only robots a lab has tested are ranked.
The highest score today is 8.4.
Is the Coway Airmega 400S right for your home? Find out in 7 questions →
Before you buy, compare it with 2 recommended alternatives
Beside it, two models on sale today that come closest to it on score and price, with the same kind of station where we have them.
Green is the best of these 3, also when they share the lead.
| This model Coway Airmega 400S | Much better, not pricier Blueair Blue Pure 311i+ Max Best on 2 facts | Higher score, 69% cheaper Blueair Blue Pure 311i Max Best on 2 facts | |
|---|---|---|---|
| Price and ranking | |||
| Lowest price | $749Coway (brand store) | $224Blueair (brand store) best | $229Blueair (brand store) |
| Score | best | best | |
| Rank | rank 9 of 9 for open-plan spaces | rank 2 of 9 for open-plan spaces | rank 1 of 9 for open-plan spaces |
| Customer rating | – | – | – |
| Station | |||
| Room size same on all | open-plan spaces | open-plan spaces | open-plan spaces |
| Size, noise and age | |||
| Height lower is better | – | 21 in (53.3 cm) | 19 in (48.3 cm) best |
| On the market since | October 2025 | April 2025 | December 2024 |
Facts as the maker states them. A dash means the maker does not name it. Each model’s page gives the source of every fact. Noise is the maker’s own figure, so we do not judge it, and a customer rating only counts from 20 reviews.
Prices per store
On October 15, 2026 the lowest price for the Coway Airmega 400S is $749 at Coway (brand store), shipping to the United States included. In our ranking it is rank 9 of 9 for open-plan spaces, with a score of 5.0 out of 10.
All prices include shipping to the United States. Sales tax is added at checkout. We may earn a commission when you buy through these links. It never changes our ranking.
Coway (brand store)gray Coway (brand store)white $749
Shippingabout 3–7 days
Returns–
Price history
Lowest price per day Tap a store to hide or show its line.
Lowest since Oct 14$749
Highest since Oct 14$749
Price drops since Oct 140no drop seen yet
Coway Airmega 400S specifications
The numbers that matter first, then every fact by group. As published by the maker or the store we read it from.
Coway · on the market since October 2025
Clean air delivery rate (CADR)328 cfm
Room size we compare on499 ft²
Noise at the lowest speed22 dB
Filter life6 months
Power at the highest speed66 W
Running cost: Filters: about $129 a year at today’s prices.
Consumables: The filter lasts about 6 months.
Cleaning performance 6 facts
- Clean air delivery rate (CADR)
How much clean air the purifier delivers an hour, measured with smoke, dust and pollen. A higher figure cleans a bigger room or the same room faster.
- 328 cfm (557 m³/h)
- CADR measured to
The test the CADR comes from. AHAM AC-1 and the DOE test are independent and comparable. A maker's own test is not.
- Not stated
- CADR for smoke
The CADR measured with tobacco smoke, the finest of the three test particles. It is the figure to read for wildfire smoke.
- 328 cfm (557 m³/h)
- CADR for dust
The CADR measured with dust.
- 328 cfm (557 m³/h)
- CADR for pollen
The CADR measured with pollen.
- 400 cfm (680 m³/h)
- Room size we compare on
The room size where the purifier changes the air 4.8 times an hour under a 2.5 m ceiling, worked out from its CADR. We use it so every model is compared on the same rule.
- 499 ft² (46 m²)
Filter 1 fact
- Activated carbon filter
A filter of activated carbon that takes out smells and some gases. It does not catch particles.
- yes
Running costs 1 fact
- Filter life
How long the maker says a filter lasts, in months of normal use. A filter that is spent cleans less.
- 6 months
Noise and power 3 facts
- Noise at the lowest speed
The sound level at the lowest speed, as the maker measures it.
- 22 dB
- Noise at the highest speed
The sound level at the highest speed, as the maker measures it.
- 52 dB
- Power at the highest speed
The power the purifier draws at its highest speed.
- 66 W
Air quality sensing 1 fact
- Automatic mode
The fan speed follows the air quality the sensor reads.
- yes
Smart features and warranty 1 fact
- App control
- Wi-Fi
Build 1 fact
- Weight
What the robot weighs. It counts most if you carry it up a staircase every day.
- 24.7 lb (11.2 kg)
Sources: cowaymega.com
Our score
Confidence: medium. One lab and fewer than 300 owners’ ratings. The highest score today is 8.4.
-
Lab tests 60%–
Left out, so the other parts count for more.
-
Owners’ ratings 25%–
Owners’ ratings, 25%: none yet at the stores that ship to the United States, so this part is left out and the others count for more.
-
Features 15%5.0
32 of 64 points for the facts the maker states.
- Price never countsA sale can’t lift a model. Today’s lowest price sits beside the score, checked every morning.
- No test, no rankOnly robots a lab has tested are ranked. The rest get a provisional score.
- Reviewers beside, not insideReviewers’ picks are shown next to the score and do not count in it.
Frequently asked questions about the Coway Airmega 400S
What size of room is the Coway Airmega 400S for?
The Coway Airmega 400S is sized for a room of about 499 ft², the room size we compare it on. Its clean air delivery rate (CADR) is 328 cfm.
How often does the Coway Airmega 400S need a new filter?
The maker gives the filter a life of 6 months.
How loud is the Coway Airmega 400S?
The maker states 22 dB at the lowest speed and 52 dB at the highest.
Is the Coway Airmega 400S good for wildfire smoke?
Its CADR for smoke is 328 cfm. A higher number clears smoke from a room faster, so compare it with the size of your room.
The maker
Coway
Coway began in Korea in 1989 and describes itself as a global company with three decades focused on health. In the United States it sells Airmega air purifiers, Bidetmega bidet toilet seats and Aquamega water purifiers.
