Details come from the older review, the maker’s claims and the Amazon listing, checked on October 14, 2026. The older review and the listing use different air-change rates for coverage, so both are explained. Noise and CADR figures come from the older review and were not retested.
The Coway Airmega 400 is one of the strongest home air purifiers. Here is what it does, how big a room it really cleans and what it costs to run.
Table of Contents
What You Get
Price on Amazon: $633.69 | 4.6 stars from 2,210 ratings (checked October 14, 2026)
Design and Size
The Airmega 400 is a tall tower in silver and graphite or white. The older review said it is about 23 inches tall and 15 inches wide and deep, and weighs about 25 pounds. It has handles on both sides and a touch panel. It looks modern and plain, and it needs a little floor space. Plastic covers protect the filters and the fan outlet.
Looking ahead, big home purifiers like the Coway Airmega 400 are moving from a luxury to a normal buy for homes with wildfire smoke, pets or allergies. Prices have held firm at the top end, around $630 on Amazon now, and makers add app control and subscription filters. The catch is that the filter bill can add up fast over a 10-year life.
How It Works
- Smart mode. A sensor reads the air and changes the fan speed on its own.
- Sleep mode. If the room is dark and the air stays clean for about 3 minutes, it drops to the lowest speed.
- Eco mode. If the air stays clean for about 10 minutes (30 per the listing), the fan turns off and returns when needed.
- Air quality light. A color-coded display shows the air in real time.
- Timer. Off after 1, 4 or 8 hours.
- Filters. A washable pre-filter and a combined HEPA and carbon filter, with lights that count down from 100 percent.
- Warranty. 5 years limited on the electrical parts and motor.
The risk to watch is the coverage claim. The older review said the Airmega 400 cleans about 624 square feet, about five times an hour. The listing says up to 3,120 square feet in 60 minutes, which is one air change an hour at an 8 foot ceiling. Both are true, but only the smaller number is useful for allergies or smoke. Expect more listings that lead with the larger number. Size the unit by the five-times-an-hour figure, and budget for filters once a year.
Noise, CADR and Real Coverage
The older review measured about 55 dB on high, about 39 dB on a middle setting and 22 dB at the lowest. It gave 410 CFM of airflow and a CADR of about 350 for dust, smoke and pollen. At five air changes an hour, the older review put the room size at about 624 square feet. The listing says up to 3,120 square feet in 60 minutes, which is about one change per hour. Read what CADR means and compare with air purifiers for large rooms.
Filter Cost
The older review said two filters cost about $200 a year. On Amazon today the replacement filter set, a Max2 green HEPA and carbon pair, is $94.31 and lasts up to about a year. You can also rinse the pre-filter. Use the air purifier filter replacement cost guide to plan the cost over five years.
Airmega 400 vs Other Big Purifiers
The older review named the AirDoctor 5000 and the AirDog X8 as the main rivals. See our AirDoctor vs Coway comparison. For a smaller, cheaper Coway, read the Coway Mighty review.
Prices and Alternatives on Amazon
Prices and ratings were checked on Amazon on October 14, 2026.
Price on Amazon: $633.69 | 4.6 stars from 2,210 ratings (checked October 14, 2026)
The Coway Airmega 400 is listed for spaces up to 3,120 square feet in 60 minutes, with a washable pre-filter, a HEPA filter, auto and sleep modes, a timer and a 5-year warranty. It has a 4.6 rating from over 2,200 ratings.
Price on Amazon: $229.99 | 4.6 stars from 29,221 ratings (checked October 14, 2026)
The Coway Mighty AP-1512HH is listed for up to 1,748 square feet with an air quality monitor, auto and eco modes and a 3-year warranty. It has a 4.6 rating from over 29,000 ratings.
Price on Amazon: $169.99 | 4.5 stars from 2,572 ratings (checked October 14, 2026)
The Blueair Blue Pure 311i Max is listed for up to 2,107 square feet with Wi-Fi, auto mode and 23 dB quiet filtration. It has a 4.5 rating from over 2,500 ratings.
Price on Amazon: $179.99 | 4.6 stars from 32,412 ratings (checked October 14, 2026)
The Winix 5510 is listed for up to 1,881 square feet in one hour, with true HEPA, a carbon filter and app support. It has a 4.6 rating from over 32,000 ratings.
Pros and Cons
Pros: strong airflow for large rooms; auto, eco and sleep modes; real-time air quality light; washable pre-filter; 5-year warranty; down to 22 dB on low.
Cons: high price; about 55 dB on high; heavy, with a large footprint; yearly filter cost; coverage claims are confusing.
FAQ
How big a room does the Coway Airmega 400 clean?
About 624 square feet at five air changes an hour, per the older review. The listing says up to 3,120 square feet in 60 minutes.
How loud is it?
About 55 dB on high, 39 dB on a middle setting and 22 dB at the lowest, per the older review.
How much do the filters cost?
The replacement filter set is $94.31 on Amazon today and lasts up to about a year.
Does it have a warranty?
Yes, 5 years limited, per the listing and the older review.
Final Word
The Airmega 400 is a strong choice for a large room or a smoky home. For a smaller room, a Coway Mighty or a Blueair costs far less.
What happens next: expect more big towers with app control, air quality displays and filter subscriptions. If you have a large open room or a smoke problem, the Airmega 400 class still makes sense.
Related Guides
Keep going with Coway Mighty review, AirDoctor vs Coway, air purifiers for large rooms, air purifier filter replacement cost guide and what CADR means.
