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How Much Concrete for an 8x22 Slab?

How much concrete for an 8x22 slab depends on thickness. The slab covers 8 × 22 = 176 square feet, and at 4 inches thick that is about 2.17 cubic yards, or 2.39 yards with a 10 percent allowance. Mixed from bags, it is roughly 98 bags of 80 lb mix.

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The math for an 8x22 slab

  1. Area: 8 ft × 22 ft = 176 sq ft.
  2. Thickness in feet: 4 in ÷ 12 = 0.333 ft.
  3. Volume: 176 × 0.333 = 58.7 cubic feet.
  4. Cubic yards: 58.7 ÷ 27 = 2.17 yd³.
  5. With 10% extra: 2.39 yd³.

The concrete calculator runs the same steps for any size and thickness.

Concrete for an 8x22 slab by thickness

ThicknessCubic feetCubic yardsYards +10%80 lb bags60 lb bags
4 in58.72.172.3998131
5 in73.32.722.99123163
6 in88.03.263.59147196

Bag counts assume about 0.60 cubic feet per 80 lb bag and 0.45 per 60 lb bag, rounded up.

Thickness for this job

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.

Truck or bags?

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.

Base and forms

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

Plan the joints before the pour. Panels close to square crack less than long, narrow ones, and joint spacing around 8 feet is typical for a 4-inch slab. Cut joints with a groover while the concrete is soft or with a saw within the first day.

Questions people ask

How many yards of concrete for an 8x22 slab at 4 inches?

About 2.17 cubic yards, or 2.39 with 10 percent extra.

How many yards for an 8x22 slab at 6 inches?

About 3.26 cubic yards.

How many 80 lb bags for an 8x22 slab?

About 98 bags at 4 inches thick, before any waste allowance.

How many square feet is an 8x22 slab?

176 square feet.

How many 80 lb bags make a cubic yard?

About 45. Each 80 lb bag yields roughly 0.6 cubic feet, and a cubic yard is 27 cubic feet.

How thick should the base under the slab be?

About 4 inches of compacted gravel is common for residential slabs, more on soft or poorly drained soil.

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