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How Much Concrete for a 14x36 Slab?

How much concrete for a 14x36 slab depends on thickness. The slab covers 14 × 36 = 504 square feet, and at 4 inches thick that is about 6.22 cubic yards, or 6.84 yards with a 10 percent allowance. Mixed from bags, it is roughly 280 bags of 80 lb mix.

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The math for a 14x36 slab

  1. Area: 14 ft × 36 ft = 504 sq ft.
  2. Thickness in feet: 4 in ÷ 12 = 0.333 ft.
  3. Volume: 504 × 0.333 = 168.0 cubic feet.
  4. Cubic yards: 168.0 ÷ 27 = 6.22 yd³.
  5. With 10% extra: 6.84 yd³.

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

Concrete for a 14x36 slab by thickness

ThicknessCubic feetCubic yardsYards +10%80 lb bags60 lb bags
4 in168.06.226.84280374
5 in210.07.788.56350467
6 in252.09.3310.27420560

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.

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

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 8 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 14x36 slab at 4 inches?

About 6.22 cubic yards, or 6.84 with 10 percent extra.

How many yards for a 14x36 slab at 6 inches?

About 9.33 cubic yards.

How many 80 lb bags for a 14x36 slab?

About 280 bags at 4 inches thick, before any waste allowance.

How many square feet is a 14x36 slab?

504 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.

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.

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