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How Much Concrete for a 14x24 Garage Slab?

A 14 by 24 foot garage slab is 336 square feet. How much concrete for a 14x24 garage slab at the common 5-inch thickness: about 5.19 cubic yards. Most people order 5.75 yards to cover waste and an uneven base.

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The math for a 14x24 garage slab

  1. Area: 14 ft × 24 ft = 336 sq ft.
  2. Thickness in feet: 5 in ÷ 12 = 0.417 ft.
  3. Volume: 336 × 0.417 = 140.0 cubic feet.
  4. Cubic yards: 140.0 ÷ 27 = 5.19 yd³.
  5. With 10% extra: 5.70 yd³.

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

Concrete for a 14x24 garage slab by thickness

ThicknessCubic feetCubic yardsYards +10%80 lb bags60 lb bags
4 in112.04.154.56187249
5 in140.05.195.70234312
6 in168.06.226.84280374

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

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.

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.

Getting the ground ready

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 garage 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.

Keeping cracks under control

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 12 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 14x24 garage slab at 4 inches?

About 4.15 cubic yards, or 4.56 with 10 percent extra.

How many yards for a 14x24 garage slab at 6 inches?

About 6.22 cubic yards.

How many 80 lb bags for a 14x24 garage slab?

About 187 bags at 4 inches thick, before any waste allowance.

How many square feet is a 14x24 garage slab?

336 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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