Sizing
What size humidifier for 800 square feet
2.7 gallons a day at an 8 ft ceiling, 3.0 at 9 ft. That is more than most large-tank portables move at the setting whose run time they publish.
By Scooter M. · Published · Updated
We earn a commission if you buy through the links on this page, at no extra cost to you. It does not change what we recommend or the order the picks appear in. Full disclosure. We show a live price when we have one and the words “Check price” when we do not. We never print a number we cannot currently verify.
| # | Product | Best for | Gal/day | Price |
|---|---|---|---|---|
| 1 | No image Vornado Evap40Top pickVornado publishes an output figure and a coverage figure, and the two agree. Four gallons a day covers about 1,180 sq ft at our derived rate against a 1,000 sq ft claim. | The only coverage claim here the arithmetic supports | 4.0published · 1,184 sq ft | Check price#ad |
| 2 | No image Levoit LV600S HybridWarm and cool mist from a 6-liter tank, and the only Levoit in this set that publishes a maximum output. On warm mist it genuinely covers a floor of a house. | The one unit here that publishes an output figure | 3.5published · 1,033 sq ft | Check price#ad |
| 3 | No image Levoit Superior 6000SSix gallons, evaporative, and a Dry Mode that dries the wicks between runs. The 3,000 sq ft claim needs five times the output its own run time implies. | Mist-free humidification with a drying cycle | 2.0implied · 592 sq ft | Check price#ad |
| 4 | No image AIRCARE MA1201 ConsoleA 3.6-gallon console on casters with four speeds and a full-size SuperWick. The nearest thing to a whole-house humidifier you can plug in. | Moving serious water without touching the ductwork | 2.4implied · 710 sq ft | Check price#ad |
Eight hundred square feet is the size of a generous one-bedroom apartment or a large open living space, and it is right at the point where the tank-versus-output distinction starts costing people money.
We earn a commission if you buy through the links on this page, at no extra cost to you. It does not change what we recommend or the order the picks appear in. Full disclosure. We show a live price when we have one and the words “Check price” when we do not. We never print a number we cannot currently verify.
| # | Product | Best for | Gal/day | Price |
|---|---|---|---|---|
| 1 | No image Vornado Evap40Top pickVornado publishes an output figure and a coverage figure, and the two agree. Four gallons a day covers about 1,180 sq ft at our derived rate against a 1,000 sq ft claim. | The only coverage claim here the arithmetic supports | 4.0published · 1,184 sq ft | Check price#ad |
| 2 | No image Levoit LV600S HybridWarm and cool mist from a 6-liter tank, and the only Levoit in this set that publishes a maximum output. On warm mist it genuinely covers a floor of a house. | The one unit here that publishes an output figure | 3.5published · 1,033 sq ft | Check price#ad |
| 3 | No image Levoit Superior 6000SSix gallons, evaporative, and a Dry Mode that dries the wicks between runs. The 3,000 sq ft claim needs five times the output its own run time implies. | Mist-free humidification with a drying cycle | 2.0implied · 592 sq ft | Check price#ad |
| 4 | No image AIRCARE MA1201 ConsoleA 3.6-gallon console on casters with four speeds and a full-size SuperWick. The nearest thing to a whole-house humidifier you can plug in. | Moving serious water without touching the ductwork | 2.4implied · 710 sq ft | Check price#ad |
Why a big tank is not the answer here
Search for a humidifier at this size and you will be shown 6 and 10 liter tanks with coverage claims comfortably above 800 square feet. Two of those claims are in our set.
| Unit | Tank | Claim | Output (published or implied) |
|---|---|---|---|
| Levoit OasisMist 1000S | 2.6 gal / 10 L | 600 sq ft | 0.62 implied on low |
| Levoit Classic 300S | 1.58 gal / 6 L | 505 sq ft | 0.63 implied on low |
| Levoit LV600S | 1.58 gal / 6 L | 753 sq ft | 3.49 published, max warm mist |
| Levoit Superior 6000S | 6 gal / 22.7 L | 3,000 sq ft | 2.0 implied on low |
| Vornado Evap40 | 4 gal | 1,000 sq ft | 4.0 published, continuous on high |
The 10 liter OasisMist 1000S has four times the reservoir of the 6 liter LV600S and, on the figures each maker publishes, roughly a sixth of the daily output. That is not a defect in the 1000S - it is a machine built to run quietly for four nights, and it does that well. It is a demonstration that tank size and output are unrelated quantities that the category presents as though they were the same one.
The two units that clear it on published data
The Vornado Evap40 publishes up to 4 gallons a day on high against a 1,000 square foot claim, and 4 gallons covers about 1,180 square feet at our rate. It has margin at 800. The Levoit LV600S publishes 550 mL an hour on maximum warm mist, which is 3.49 gallons a day, so it clears 2.70 comfortably - but only with the heater running, at 280 watts, emptying its 6 liter tank in about eleven hours.
That trade is worth thinking about before you buy. The full electricity arithmetic is on running cost; the short version is that a 280 W unit run overnight all winter costs real money, and a 30 W evaporative one does not.
The layout question
Eight hundred square feet in one open room is a different problem from 800 square feet across four rooms off a hallway. Moisture does not travel through closed doors, so:
- If it is genuinely open, size for the whole volume and put the unit somewhere air moves.
- If it is a hallway with rooms off it, you are not sizing for 800 square feet. You are sizing for the room you are in, and probably for a second unit in the bedroom.
- If you keep the bedroom door shut at night - most people do - that room needs its own machine regardless of what the rest of the floor has. See bedroom sizing.
What to check on any unit you are considering
- Find the published tank capacity and the published run time. Note which setting the run time is for - it is nearly always the lowest.
- Compute tank divided by run time, times 24. That is the implied output at that setting.
- Compare it against 2.70 gallons a day. If it is well under, the machine will hold humidity in a bedroom, not in your 800 square feet.
- Look for a published maximum output. If there is one, use it. If there is not, treat the coverage claim as marketing rather than a specification.
The picks, in full
image
Top pick · The only coverage claim here the arithmetic supports
Vornado Evap40
Vornado publishes an output figure and a coverage figure, and the two agree. Four gallons a day covers about 1,180 sq ft at our derived rate against a 1,000 sq ft claim.
Run the check that fails everywhere else on this page and it passes here. Four gallons a day at 296 square feet per gallon per day is about 1,180 square feet of coverage, against a claim of 1,000. Vornado left itself margin instead of taking it.
It passes because it is evaporative. A wick and a fan can only put as much water into the air as the air will accept, which is why an evaporative unit self-limits near 50% relative humidity and why it cannot produce white dust: the minerals stay in the wick. The EPA's guidance to use low-mineral water exists mainly because ultrasonic and impeller units disperse what is dissolved in the tank, and this design does not.
The cost of that is the wick. Two of them, on a schedule Vornado does not publish, which is the recurring bill an ultrasonic unit does not have. Whether that trade is worth it is arithmetic, and it is worked through in full on our filter-cost page.
What works
- Publishes an output figure, and the coverage claim survives being checked against it
- Evaporative, so it cannot produce white dust and self-limits near a safe humidity
- Five-year warranty, the longest published here
What does not
- Two wicks to replace on an interval Vornado does not publish
- A fan moving air across a wet wick is audible, and no dB figure is published
- No rated wattage published
Skip this ifyou want silence. Every evaporative unit is a fan, and Vornado publishes no noise figure for this one.
The arithmetic
- Published output (continuous on high)
- 4.0 gal/day
- Covers, at 296 sq ft per gal/day
- 1,184 sq ft
- Maker’s coverage claim
- 1,000 sq ft
- Output that claim would need
- 3.4 gal/day
Output as the manufacturer publishes it. Coverage rate derived from Aprilaire’s own published capacity-and-coverage pairs.
Published specification
- Tank
- 4 galSource
- Output/day
- Up to 4 galVornado's wording: up to a 4 gallon water output when operated continuously on highSource
- Coverage
- Up to 1,000 sq ftSupported by its own published output. This is the only unit in the set where that is true.Source
- Run time
- not publishedVornado publishes output instead, which is more useful
- Power
- not published
- Filter
- Two humidifying wicksTwo are supplied, one front and one rear. No replacement interval is published.Source
- Cleaning
- Vornado states easy to clean and operateSource
image
Pick 2 · The one unit here that publishes an output figure
Levoit LV600S Hybrid
Warm and cool mist from a 6-liter tank, and the only Levoit in this set that publishes a maximum output. On warm mist it genuinely covers a floor of a house.
This is the only unit in the portable group whose maker publishes an output rate, and publishing it is worth crediting. 550 mL an hour is 13.2 liters a day, which is 3.49 gallons a day, which covers roughly 1,030 square feet at our derived rate. That is more than its own 753 sq ft claim, so for once the box is conservative.
The catch is the setting. 3.49 gallons a day on maximum warm mist empties a 6-liter tank in about eleven hours and draws 280 watts while it does it. On the lowest setting the same machine moves 0.76 gallons a day and covers about 224 square feet. One box, a four-and-a-half-fold range, and only the two ends published.
280 watts is the number to think about if you plan to run warm mist all winter. Boiling water is not free, and this is the page where that becomes a real line on a bill rather than a footnote.
What works
- Publishes an actual output rate, which almost nobody in this category does
- Warm mist is genuinely useful in a cold room and slightly reduces microbial growth in the tank
- 6 liters with a 753 sq ft claim that its own maximum output can actually support
What does not
- 280 W rated: warm mist all season is a real electricity cost, not a rounding error
- Maximum output empties the tank in about eleven hours
- The gap between lowest and highest setting is roughly 4.5x, and only the two extremes are published
Skip this ifyou want to run it flat out overnight and forget it. At the published maximum it needs refilling before morning.
The arithmetic
- Published output (lowest mist)
- 3.5 gal/day
- Covers, at 296 sq ft per gal/day
- 1,033 sq ft
- Maker’s coverage claim
- 753 sq ft
- Output that claim would need
- 2.5 gal/day
Output as the manufacturer publishes it. Coverage rate derived from Aprilaire’s own published capacity-and-coverage pairs.
Published specification
- Tank
- 1.58 gal / 6 LSource
- Output/day
- 550 mL/h max warm mistLevoit publishes this as an hourly rate. Over 24 hours that is 13.2 L, or 3.49 gallons per day.Source
- Coverage
- 430-753 sq ft / 40-70 m2Source
- Run time
- Up to 50 hOn the lowest mist settingSource
- Power
- 280 WThe heater dominates. Cool mist alone draws far less.Source
- Filter
- Water filter sponge, 2 suppliedA sponge, not a wick. No scheduled replacement interval is published.Source
- Cleaning
- Descaling pads sold separatelySource
image
Pick 3 · Mist-free humidification with a drying cycle
Levoit Superior 6000S
Six gallons, evaporative, and a Dry Mode that dries the wicks between runs. The 3,000 sq ft claim needs five times the output its own run time implies.
Six gallons over 72 hours is two gallons a day, which covers about 590 square feet. The box says 3,000. To actually hold humidity across 3,000 square feet this unit would need to move a little over ten gallons a day, and at that rate its six-gallon reservoir would run dry in about fourteen hours. Both numbers describe the machine; only one describes it at a time, and the maker publishes no figure that reconciles them.
Dry Mode is the genuinely good idea here and it deserves credit. A wet wick sitting in a warm room is the substrate for everything the EPA warns about, and a fan cycle that dries the wicks between runs attacks that problem directly rather than adding an antimicrobial coating and hoping. It also extends wick life, which is the recurring cost.
Thirty watts to move two gallons a day is efficient, and mist-free operation means the minerals stay in the wicks rather than settling on your furniture. If you can live with a coverage claim you should mentally divide by five, this is a well-made machine.
What works
- Dry Mode addresses the real failure mode of evaporative units instead of masking it
- Mist-free, so no white dust whatever your water is like
- 30 W for six gallons of capacity, with noise published at both ends of the range
What does not
- The 3,000 sq ft claim is about five times what the published tank and run time imply
- Four wicks to replace, on an interval Levoit does not publish
- 45 dB at the top of the fan range is audible in a quiet bedroom
Skip this ifyou bought it for the 3,000 sq ft number. Size it at around 600 square feet on the setting whose run time Levoit actually publishes.
The arithmetic
- Implied output (low fan speed)
- 2.0 gal/day
- Covers, at 296 sq ft per gal/day
- 592 sq ft
- Maker’s coverage claim
- 3,000 sq ft
- Output that claim would need
- 10.1 gal/day
Output derived as tank capacity divided by published run time, times 24. Coverage rate derived from Aprilaire’s own published capacity-and-coverage pairs.
Published specification
- Tank
- 6 gal / 22.7 LSource
- Output/day
- not published
- Coverage
- 3,000 sq ft / 279 m23,000 sq ft needs about 10.1 gal/day at our derived rate. Its published tank and run time imply 2.0.Source
- Run time
- Up to 72 hOn the low fan speedSource
- Power
- 30 WSource
- Noise
- 28-45 dBSource
- Filter
- Four wick filters, pre-installedReplacements are sold by Levoit as a four-pack. No replacement interval is published.Source
- Cleaning
- Dry ModeLevoit's own wording: low and high fan speeds dry out the elevated wick filters, extending filter lifeSource
image
Pick 4 · Moving serious water without touching the ductwork
AIRCARE MA1201 Console
A 3.6-gallon console on casters with four speeds and a full-size SuperWick. The nearest thing to a whole-house humidifier you can plug in.
This one needs care, because the two published figures describe opposite ends of the machine and AIRCARE prints neither of the numbers that would join them up. A 3.6-gallon tank lasting 36 hours is 2.4 gallons a day, or about 710 square feet. Covering the claimed 3,600 square feet would take roughly 12.2 gallons a day, at which rate the same tank empties in about seven hours.
Both can be true at once: 36 hours will be the lowest of the four fan speeds and 3,600 square feet the highest. The problem is that the maker publishes the endurance of one setting and the coverage of another and no output figure at all, so nothing on the page lets a buyer connect them. Retail listings do quote 12 gallons a day; we are not treating a retailer's number as a manufacturer specification.
Taken on its own terms it is a lot of machine. Four speeds, casters, a detachable bottle you fill at a tap rather than carrying the whole unit, and a full-size SuperWick that catches minerals instead of dispersing them. Size it by the setting you will actually run, and expect to refill it daily if that setting is a high one.
What works
- Genuinely large capacity in a plug-in unit, with four speeds to place it
- MAF1 SuperWick captures minerals, so no white dust
- Detachable bottle and casters make refilling a two-minute job rather than a chore
What does not
- No published output figure anywhere on the manufacturer page
- The 3,600 sq ft claim and the 36-hour run time cannot both describe the same setting
- A console this size is furniture, and it is loud enough to be noticed on the upper speeds
Skip this ifyou want a bedroom unit. This is a living-room-sized appliance and it is not pretending otherwise.
The arithmetic
- Implied output (maximum published run time)
- 2.4 gal/day
- Covers, at 296 sq ft per gal/day
- 710 sq ft
- Maker’s coverage claim
- 3,600 sq ft
- Output that claim would need
- 12.2 gal/day
Output derived as tank capacity divided by published run time, times 24. Coverage rate derived from Aprilaire’s own published capacity-and-coverage pairs.
Published specification
- Tank
- 3.6 galSource
- Output/day
- not publishedRetailers state 12 gal/day. AIRCARE's own product page does not, so we do not treat it as a published figure.
- Coverage
- Up to 3,600 sq ft3,600 sq ft needs about 12.2 gal/day at our derived rate. AIRCARE publishes no output figure, so the claim cannot be checked against its own data.Source
- Run time
- Up to 36 hSource
- Power
- not published
- Filter
- MAF1 SuperWickSource
- Cleaning
- Evaporative wick traps mineral depositsDetachable water bottle for filling; castersSource
Questions people actually ask
What size humidifier for 800 square feet?
About 2.7 gallons a day at an 8 ft ceiling, 3.0 at 9 ft. In our set the Vornado Evap40 (4 gal/day published) and the Levoit LV600S (3.49 gal/day published on maximum warm mist) are the portables that clear it on manufacturer data.
Is a 6 liter humidifier enough for 800 sq ft?
It depends entirely on the model, which is the point. A 6 liter Levoit Classic 300S implies 0.63 gallons a day at the setting whose run time is published. A 6 liter Levoit LV600S publishes 3.49 gallons a day on maximum warm mist. Same tank, very different machines.
Do I need two humidifiers for 800 square feet?
If the space is open, one unit sized to 2.7 gallons a day is enough. If it is several rooms off a hallway, yes - moisture does not pass through closed doors, and a bedroom used with the door shut needs its own machine.
How often do I refill a humidifier covering 800 sq ft?
At 2.7 gallons a day, a 6 liter tank lasts about 14 hours, a 10 liter about 23 hours, and a 4 gallon unit about 36 hours. Daily refilling is normal at this size.
Sources
Every figure on this page came from one of the documents below, read on the date shown. We do not cite other review sites, forum posts or video reviews as sources of fact.
- Vornado Evap40 - manufacturer spec page (retrieved September 1, 2026)
- Levoit LV600S - manufacturer spec page (retrieved September 1, 2026)
- Levoit OasisMist 1000S - manufacturer spec page (retrieved September 1, 2026)
- Levoit Classic 300S - manufacturer spec page (retrieved September 1, 2026)
- Levoit Superior 6000S - manufacturer spec page (retrieved September 1, 2026)
Read next
Humidifier sizing chart by square footage
The sizing chart in gallons per day, by floor area and ceiling height, with a companion table of what each figure means in practice.
1,000 sq ft
What size humidifier for 1,000 sq ft
The 1,000 sq ft requirement worked out in gallons per day, and the units whose published output can actually meet it.
Top pick: Vornado Evap40 · 4.0 gal/day
Best for large rooms
Best humidifiers for large rooms
Large-room picks, chosen on whether the published output reaches the requirement rather than on what the box claims.
Top pick: Vornado Evap40 · 4.0 gal/day
Found a number that is wrong? Tell us and we will fix it and say so. How we pick shows every formula used on this page.