How Much Concrete for a 20x22 Garage Slab?
A 20 by 22 foot garage slab is 440 square feet. How much concrete for a 20x22 garage slab at the common 5-inch thickness: about 6.79 cubic yards. Most people order 7.50 yards to cover waste and an uneven base.
Concrete calculator →The math for a 20x22 garage slab
- Area: 20 ft × 22 ft = 440 sq ft.
- Thickness in feet: 5 in ÷ 12 = 0.417 ft.
- Volume: 440 × 0.417 = 183.3 cubic feet.
- Cubic yards: 183.3 ÷ 27 = 6.79 yd³.
- With 10% extra: 7.47 yd³.
The concrete calculator runs the same steps for any size and thickness.
Related: How Much Concrete for a 12x20 Garage Slab?
Concrete for a 20x22 garage slab by thickness
| Thickness | Cubic feet | Cubic yards | Yards +10% | 80 lb bags | 60 lb bags |
|---|---|---|---|---|---|
| 4 in | 146.7 | 5.43 | 5.98 | 245 | 326 |
| 5 in | 183.3 | 6.79 | 7.47 | 306 | 408 |
| 6 in | 220.0 | 8.15 | 8.96 | 367 | 489 |
Bag counts assume about 0.60 cubic feet per 80 lb bag and 0.45 per 60 lb bag, rounded up.
Choosing the thickness
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 Garage Slab?
Ordering ready-mix
Ready-mix is priced and batched by the cubic yard (27 cubic feet). Plants commonly add a small-load fee when an order is under a set minimum, so ask about it when you call. Ordering a little extra costs far less than a second truck.
Prep before the pour
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.
Joints and reinforcement
Reinforcement does not stop cracks, but it holds them tight. Wire mesh or rebar set mid-depth on chairs is common for a garage slab that carries vehicles; fiber-reinforced mix is an option for light-duty slabs. Joints about 12 feet apart control where cracks form.
Questions people ask
How many yards of concrete for a 20x22 garage slab at 4 inches?
About 5.43 cubic yards, or 5.98 with 10 percent extra.
How many yards for a 20x22 garage slab at 6 inches?
About 8.15 cubic yards.
How many 80 lb bags for a 20x22 garage slab?
About 245 bags at 4 inches thick, before any waste allowance.
How many square feet is a 20x22 garage slab?
440 square feet.
Should I add extra for waste?
Yes. Adding 5 to 10 percent covers uneven base, spillage and form bulges.
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 16x24 Garage Slab?
- How Much Concrete for a 20x20 Garage Slab?
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