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How Much Concrete for a 6x24 Slab?

A 6 by 24 foot slab is 144 square feet. How much concrete for a 6x24 slab at the common 4-inch thickness: about 1.78 cubic yards. Most people order 2.00 yards to cover waste and an uneven base.

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The math for a 6x24 slab

  1. Area: 6 ft × 24 ft = 144 sq ft.
  2. Thickness in feet: 4 in ÷ 12 = 0.333 ft.
  3. Volume: 144 × 0.333 = 48.0 cubic feet.
  4. Cubic yards: 48.0 ÷ 27 = 1.78 yd³.
  5. With 10% extra: 1.96 yd³.

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

Concrete for a 6x24 slab by thickness

ThicknessCubic feetCubic yardsYards +10%80 lb bags60 lb bags
4 in48.01.781.9680107
5 in60.02.222.44100134
6 in72.02.672.93120160

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

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.

Getting the ground ready

Prep matters as much as the yardage. Strip sod and soft soil, compact the subgrade, then add a compacted stone base, commonly about 4 inches. A level, firm base also keeps your thickness even, which keeps the yardage close to the math.

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 a 6x24 slab at 4 inches?

About 1.78 cubic yards, or 1.96 with 10 percent extra.

How many yards for a 6x24 slab at 6 inches?

About 2.67 cubic yards.

How many 80 lb bags for a 6x24 slab?

About 80 bags at 4 inches thick, before any waste allowance.

How many square feet is a 6x24 slab?

144 square feet.

How much does a cubic yard of concrete weigh?

Roughly 4,000 pounds, or about 2 tons, for normal-weight concrete.

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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