What size shop vac you need: 4, 6, 9, 12 or 16 gallons
Shop vacs are sold by drum size, from about 1 gallon to 16 and more, and the bigger number is not always the better choice. What size do you actually need? This page sizes the drum from the job: how much water a spill or flooded floor holds, worked out from its area and depth, and how many drum-loads that is for each size.
What we compared and why
- Water per job. A wet job is a volume of water. Area times depth tells you roughly how much, and so how many times a drum fills.
- Where you empty it. A full drum is heavy. Near a floor drain a big drum is easy; upstairs, a smaller drum you empty more often is easier.
- Storage and moving it. Drum size sets the footprint and height of the vac in your garage or closet.
- Hose and cord. Reach from the outlet and from where the vac stands, stated in the listing where given.
The models compared
| Model | Gallons | Peak HP | Hose stated | Cord stated | Blower port named |
|---|---|---|---|---|---|
| CRAFTSMAN 4 gal wet/dry vac (CMXEVBE17040) | 4.0 gal | 5 HP | Not stated in listing | Not stated in listing | Not stated in listing |
| CRAFTSMAN 5 gal wet/dry vac (CMXEVBE17925) | 5.0 gal | 5 HP | Not stated in listing | Not stated in listing | Not stated in listing |
| RIDGID 6 gal wet/dry vac (RT0600) | 6.0 gal | 4.25 HP | 8.0 ft | Not stated in listing | Yes |
| Armor All 8 gal wet/dry vac with blower (VBV809) | 8.0 gal | 4.5 HP | Not stated in listing | Not stated in listing | Yes |
| DEWALT 9 gal wet/dry vac with blower (DXV09PA) | 9.0 gal | 5 HP | Not stated in listing | 10 ft | Yes |
| Vacmaster 12 gal wet/dry vac with detachable blower (VBV1210) | 12.0 gal | 5 HP | Not stated in listing | Not stated in listing | Yes |
| CRAFTSMAN 16 gal wet/dry vac with detachable blower (CMXEVBE17607) | 16.0 gal | 6.5 HP | Not stated in listing | Not stated in listing | Yes |
Table values are read from each product's current Amazon listing at the time of this page's build and normalised to one unit by us. "Not stated in listing" means the listing does not give the figure; "Listing gives two values" means the listing states it two different ways, so we show neither.
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CRAFTSMAN 4 gal wet/dry vac (CMXEVBE17040)
Who it fits: Car interiors, small spills and a small storage space; the smallest drum in this table.
Skip it if: Water jobs bigger than a sink overflow; you would empty it several times.
CRAFTSMAN 5 gal wet/dry vac (CMXEVBE17925)
Who it fits: General household use, from spills to the car; full of water, the drum holds about 42 lb of water plus the vac.
Skip it if: A basement or garage floor that takes on water; a larger drum means fewer stops.
RIDGID 6 gal wet/dry vac (RT0600)
Who it fits: Garage and workshop use with a little more drum than a 5-gallon, on casters, with a stated 8-foot hose.
Skip it if: You need to carry it up and down stairs often; a drum this size holding water is heavy.
Armor All 8 gal wet/dry vac with blower (VBV809)
Who it fits: Garage use where you want a detachable blower as well as an 8-gallon drum.
Skip it if: Indoor spills only; a 4- or 5-gallon vac is smaller to store.
DEWALT 9 gal wet/dry vac with blower (DXV09PA)
Who it fits: A basement or garage that sometimes takes on water, with a blower function named in the listing.
Skip it if: Its stated cord is 10 feet; you may need an extension cord rated for the vac far from an outlet.
Vacmaster 12 gal wet/dry vac with detachable blower (VBV1210)
Who it fits: Water jobs near a floor drain, where the 12-gallon drum means fewer stops.
Skip it if: You would have to carry it full up a flight of stairs.
CRAFTSMAN 16 gal wet/dry vac with detachable blower (CMXEVBE17607)
Who it fits: The largest jobs: a flooded basement floor with a drain nearby, or a large garage.
Skip it if: Storage is tight or the vac has to go upstairs; it is the largest drum here.
Size the drum from the water, not the HP
Most shop vac jobs in a house are either dry (sawdust, leaves, a car interior) or wet (a spill, an overflow, a basement floor). Dry jobs fit almost any drum, because you empty when it suits you. Wet jobs are where drum size matters, and you can estimate them before you buy.
Water on a floor is a volume: area times depth. One cubic foot holds about 7.48 US gallons (the NIST conversion factor). So:
| Water on the floor | 1/8 in. deep | 1/4 in. deep | 1/2 in. deep |
|---|---|---|---|
| A 5 x 5 ft patch (25 sq ft) | about 2 gal | about 4 gal | about 8 gal |
| A 10 x 10 ft room (100 sq ft) | about 8 gal | about 16 gal | about 31 gal |
| A 12 x 20 ft basement area (240 sq ft) | about 19 gal | about 37 gal | about 75 gal |
To use it for your own floor: multiply length by width in feet, multiply by the depth in inches divided by 12, then multiply by 7.48. A quarter-inch of water, about the thickness of a pencil, over a 10 x 10 ft room is already some 16 gallons.
How many drum-loads that is
Divide the gallons of water by the drum size (the 5- and 8-gallon vacs in the list fall between the columns). Makers name the drum size; the water a drum takes before its float stops suction can be somewhat less, so round up.
| Job (from the table above) | 4 gal | 6 gal | 9 gal | 12 gal | 16 gal |
|---|---|---|---|---|---|
| 5 x 5 ft at 1/4 in. (about 4 gal) | 1 to 2 | 1 | 1 | 1 | 1 |
| 10 x 10 ft at 1/8 in. (about 8 gal) | 2 | 2 | 1 | 1 | 1 |
| 10 x 10 ft at 1/4 in. (about 16 gal) | 4 | 3 | 2 | 2 | 1 |
| 12 x 20 ft at 1/4 in. (about 37 gal) | 10 | 7 | 5 | 4 | 3 |
The pattern: a shallow room-sized spill means two trips with a 5- or 6-gallon vac, and a quarter-inch over the same room three or four. Beyond that, drum size starts to save real time, but only if you can empty it where it stands. Water weighs about 8.34 pounds a gallon, so a full 12-gallon drum holds about 100 pounds of water; our shop vacs for home use guide sets out the weights by drum size.
Pick a size band
- 4 to 5 gallons: car interiors, spills, a small apartment or a closet shelf. Full of water, the drum holds about 33 to 42 lb of water, so empty it before it is full if you have to carry it.
- 6 to 9 gallons: a garage or workshop, and the occasional wet floor. Usually on casters.
- 12 to 16 gallons: basements that take on water, with a floor drain nearby to empty into. Plan where it lives; it takes floor space.
- About 1 to 2 gallons, battery-powered: quick pickups in a workshop where you already own the batteries; see cordless shop vacs by battery platform.
Reading the table
Gallons, peak HP, hose and cord are what each listing states. Peak HP is a motor rating, not a suction figure, so read it as a size class within one brand. "Not stated in listing" means the listing gives no figure. We have not checked these against the makers' pages for this page, so confirm hose and cord on the box if reach matters to you.
What this page does not tell you
We do not measure suction or how much water each drum takes before its float shuts off, and we do not rank these vacs. A shop vac is for water you can reach and remove; for water that keeps coming in, the cause needs fixing first.