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How Much Concrete for an 8x60 Slab?

How much concrete for an 8x60 slab depends on thickness. The slab covers 8 × 60 = 480 square feet, and at 4 inches thick that is about 5.93 cubic yards, or 6.52 yards with a 10 percent allowance. Mixed from bags, it is roughly 267 bags of 80 lb mix.

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The math for an 8x60 slab

  1. Area: 8 ft × 60 ft = 480 sq ft.
  2. Thickness in feet: 4 in ÷ 12 = 0.333 ft.
  3. Volume: 480 × 0.333 = 160.0 cubic feet.
  4. Cubic yards: 160.0 ÷ 27 = 5.93 yd³.
  5. With 10% extra: 6.52 yd³.

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

Concrete for an 8x60 slab by thickness

ThicknessCubic feetCubic yardsYards +10%80 lb bags60 lb bags
4 in160.05.936.52267356
5 in200.07.418.15334445
6 in240.08.899.78400534

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

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.

Ordering ready-mix

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 slab.

Base and forms

Under the slab, most residential pours sit on about 4 inches of compacted gravel. The base spreads the load, drains water away and keeps the slab from cracking as the soil freezes and thaws. Compact the base in thin lifts, and dampen it just before the pour so it does not pull water out of the mix.

Joints and reinforcement

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 8x60 slab at 4 inches?

About 5.93 cubic yards, or 6.52 with 10 percent extra.

How many yards for an 8x60 slab at 6 inches?

About 8.89 cubic yards.

How many 80 lb bags for an 8x60 slab?

About 267 bags at 4 inches thick, before any waste allowance.

How many square feet is an 8x60 slab?

480 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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