How Much Concrete for an 18x22 Slab?
For an 18x22 slab poured 4 inches thick, plan on about 4.89 cubic yards of concrete. That comes from 396 square feet times 0.333 feet of depth, divided by 27. How much concrete for an 18x22 slab at other thicknesses is in the table below.
Concrete calculator →The math for an 18x22 slab
- Area: 18 ft × 22 ft = 396 sq ft.
- Thickness in feet: 4 in ÷ 12 = 0.333 ft.
- Volume: 396 × 0.333 = 132.0 cubic feet.
- Cubic yards: 132.0 ÷ 27 = 4.89 yd³.
- With 10% extra: 5.38 yd³.
The concrete calculator runs the same steps for any size and thickness.
Related: How Much Concrete for a 12x20 Slab?
Concrete for an 18x22 slab by thickness
| Thickness | Cubic feet | Cubic yards | Yards +10% | 80 lb bags | 60 lb bags |
|---|---|---|---|---|---|
| 4 in | 132.0 | 4.89 | 5.38 | 220 | 294 |
| 5 in | 165.0 | 6.11 | 6.72 | 275 | 367 |
| 6 in | 198.0 | 7.33 | 8.07 | 330 | 440 |
Bag counts assume about 0.60 cubic feet per 80 lb bag and 0.45 per 60 lb bag, rounded up.
Choosing the thickness
Four inches is the usual thickness for patios, walks and shed floors. Slabs that carry cars or a heavy hot tub are often poured at 5 to 6 inches, and edges are sometimes thickened where loads concentrate.
Related: How Much Concrete for a 12x24 Slab?
Placing the order
A cubic yard of concrete is 27 cubic feet and weighs roughly 4,000 pounds. Most ready-mix trucks carry up to about 9 to 10 yards, though local trucks and rules vary. If your total is under a yard or two, bagged mix or a short-load supplier may be cheaper.
Getting the ground ready
Uneven ground is the main reason pours run short. Every half inch of extra depth across the slab adds concrete you did not plan for. Screed the base flat, check it with a string line and set the forms to finished height before the truck arrives.
Joints, mesh and rebar
Cut or tool control joints so the slab cracks where you want it to. A common rule is spacing them, in feet, at no more than two to three times the slab thickness in inches, so about 10 feet apart for a 4-inch slab, and about a quarter of the slab depth deep.
Questions people ask
How many yards of concrete for an 18x22 slab at 4 inches?
About 4.89 cubic yards, or 5.38 with 10 percent extra.
How many yards for an 18x22 slab at 6 inches?
About 7.33 cubic yards.
How many 80 lb bags for an 18x22 slab?
About 220 bags at 4 inches thick, before any waste allowance.
How many square feet is an 18x22 slab?
396 square feet.
How much does a cubic yard of concrete weigh?
Roughly 4,000 pounds, or about 2 tons, for normal-weight concrete.
When is bagged concrete practical?
Usually for jobs under about a cubic yard. Beyond that, mixing dozens of bags by hand gets slow and batches may not blend well.
Related guides
- How Much Area Does a Yard of Concrete Cover?
- How Many Bags of Concrete in a Yard? 40, 60, 80 lb
- Gravel Base Under a Concrete Slab: Depth and Tons
- How Many Yards in a Concrete Truck? Mixer Sizes
- Concrete Short Load Fee: What It Is and How to Cut It
- 60 lb vs 80 lb Concrete Bags: Yield, Count, and Cost
- Rebar vs Wire Mesh in a Slab: Which One to Use
- Cost to Pour a Concrete Slab: Per Square Foot
- How Much Concrete for an 18x18 Slab?
- How Much Concrete for an 18x20 Slab?
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