How Much Concrete for a 12x24 Garage Slab?
A 12 by 24 foot garage slab is 288 square feet. How much concrete for a 12x24 garage slab at the common 5-inch thickness: about 4.44 cubic yards. Most people order 5.00 yards to cover waste and an uneven base.
Concrete calculator →The math for a 12x24 garage slab
- Area: 12 ft × 24 ft = 288 sq ft.
- Thickness in feet: 5 in ÷ 12 = 0.417 ft.
- Volume: 288 × 0.417 = 120.0 cubic feet.
- Cubic yards: 120.0 ÷ 27 = 4.44 yd³.
- With 10% extra: 4.89 yd³.
The concrete calculator runs the same steps for any size and thickness.
Related: How Much Concrete for a 12x24 Slab?
Concrete for a 12x24 garage slab by thickness
| Thickness | Cubic feet | Cubic yards | Yards +10% | 80 lb bags | 60 lb bags |
|---|---|---|---|---|---|
| 4 in | 96.0 | 3.56 | 3.91 | 160 | 214 |
| 5 in | 120.0 | 4.44 | 4.89 | 200 | 267 |
| 6 in | 144.0 | 5.33 | 5.87 | 240 | 320 |
Bag counts assume about 0.60 cubic feet per 80 lb bag and 0.45 per 60 lb bag, rounded up.
How thick to pour it
Garage floors are commonly 4 to 6 inches thick; 5 inches is a practical middle for cars and light trucks, and 6 inches suits heavier vehicles or a shop with equipment. Check local code, since some areas set a minimum.
Related: How Much Concrete for a 12x24 Patio?
Truck or bags?
Concrete is ordered by the cubic yard, and a yard is 27 cubic feet. Ready-mix plants usually sell in quarter- or half-yard steps, so round up to the next step rather than down. Running short in the middle of a pour leaves a cold joint, which is a weak seam in the garage slab.
Base and forms
Uneven ground is the main reason pours run short. Every half inch of extra depth across the garage 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.
Keeping cracks under control
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 a 12x24 garage slab at 4 inches?
About 3.56 cubic yards, or 3.91 with 10 percent extra.
How many yards for a 12x24 garage slab at 6 inches?
About 5.33 cubic yards.
How many 80 lb bags for a 12x24 garage slab?
About 160 bags at 4 inches thick, before any waste allowance.
How many square feet is a 12x24 garage slab?
288 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 a 12x20 Garage Slab?
- How Much Concrete for a 12x22 Garage Slab?
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