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MaterialCalc — 24x24 Garage Slab Concrete & Cost Calculator

Estimate prepared 09/01/2026. Estimates only; verify against your plans before ordering.

24x24 Garage Slab Concrete & Cost Calculator

Five inches is the usual call for a garage. Four is thin under a truck.

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Result

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24x24 is the standard two-car garage footprint — 576 square feet, and at 5 inches thick roughly ten cubic yards of concrete. That is two trucks or one large one, and it is the point where the thickened perimeter edge and the base prep cost real money alongside the concrete itself.

Assumptions used

These are the numbers behind the result. Where one of them is soft, the cost range widens rather than pretending to a precision the data does not have.

80 lb bag yield
0.6 ft³

Yield of one 80 lb bag of standard concrete mix.

Quikrete product data sheet — Published product data, checked 09/01/2026

60 lb bag yield
0.45 ft³

Yield of one 60 lb bag of standard concrete mix.

Quikrete product data sheet — Published product data, checked 09/01/2026

Ready-mix short-load threshold
1 yd³

Below roughly one cubic yard, most suppliers add a short-load fee that erases the price advantage over bags.

Regional ready-mix supplier schedules — Rough figure — widens the estimate range, checked 09/01/2026

Bags per pallet
42 bags

Above roughly one pallet of 80 lb bags, ready-mix is usually cheaper and always faster.

Home Depot / Lowe's pallet quantities — Industry standard, varies by supplier, checked 09/01/2026

Compacted gravel base under slab
4 in

Drains water away from the underside of the slab. Skipping it is the usual cause of a slab that heaves.

International Residential Code (2021) — Industry standard, varies by supplier, checked 09/01/2026

Crushed gravel density
105 lb/ft³

Compacted 3/4 in crushed stone. Varies by quarry and moisture; loose stone runs lighter.

USGS aggregate bulk density range — Industry standard, varies by supplier, checked 09/01/2026

Compaction allowance
0.2

Loose stone loses roughly a fifth of its volume once compacted, so order above the finished volume.

Standard earthwork practice — Rough figure — widens the estimate range, checked 09/01/2026

Vapor barrier roll coverage
1000 ft²

Home Depot / Lowe's published product data — Published product data, checked 09/01/2026

Welded wire mesh sheet coverage
150 ft²

One 5x10 ft sheet, less the overlap at the seams.

Home Depot / Lowe's published product data — Industry standard, varies by supplier, checked 09/01/2026

Prices verified 09/01/2026 (US national average, big-box retail shelf price and regional ready-mix quotes). Regional adjustment: Blended from RSMeans city cost index bands and BLS construction wage differentials.

The formula

576 ft² × thickness in feet ÷ 27 = cubic yards. At 5 in that is 576 × 0.4167 = 240 ft³ = 8.9 yd³ before waste. A monolithic garage slab also carries a thickened edge around the perimeter, which this figure does not include — add it separately if you are pouring the footing and slab together.

Worked examples

24x24 at 5 in, the standard build

Length: 24 Width: 24 Thickness: 5 Waste: 10

About 9.8 cubic yards with waste, plus roughly 5 tons of base. One large truck or two smaller ones — confirm the load size with your supplier before the day.

24x24 at 6 in for a shop

Length: 24 Width: 24 Thickness: 6 Waste: 10

Just under 12 yards. Worth the extra two yards if a lift, a trailer or heavy equipment will live in here — retrofitting thickness is impossible.

24x30 at 5 in, a deeper garage

Length: 24 Width: 30 Thickness: 5 Waste: 10

About 12.2 yards. Six extra feet of depth is the cheapest space you will ever add, and it is the difference between parking and parking plus a workbench.

Choosing materials

  • Five inches, not four. A 4 in garage slab handles cars but cracks under a loaded pickup or a floor jack, and the extra inch costs about a yard and a half of concrete on this footprint.
  • If you are pouring monolithically, the thickened edge around the perimeter adds concrete this calculation does not cover. A 12 in wide by 12 in deep edge around a 24x24 adds roughly 1.2 cubic yards.
  • Anchor bolts go in wet concrete, not drilled afterwards. Have them laid out and labeled before the truck arrives, because you will have about twenty minutes to set them.
  • Slope the slab a quarter inch per foot toward the door, or put in a drain. Melting snow off a truck has to go somewhere, and a flat garage floor sends it to the back wall.
  • Ten yards is a serious pour for a homeowner crew. Book a finisher for the day even if you do all the prep yourself — a garage floor that sets badly is a floor you look at every day for thirty years.

Common questions

How much concrete for a 24x24 garage slab?

At 5 inches thick, 8.9 cubic yards before waste and about 9.8 with a 10% allowance. At 4 inches it is 7.1 yards, and at 6 inches 10.7. Add roughly 1.2 yards if you are pouring a thickened perimeter edge at the same time.

How thick should a garage slab be?

Five inches for normal vehicle use, six for a shop with a lift, trailers or heavy tools. Four inches is enough for cars alone but has no margin — it is the thickness people regret when they buy a floor jack.

What does a 24x24 garage slab cost?

Material — concrete, base, mesh, vapor barrier — typically runs $2,200 to $3,400. Poured and finished by a contractor, roughly $5,800 to $9,500 depending on region and site access. Toggle labor above to compare.

Do I need a thickened edge or a separate footing?

It depends on what sits on the slab and your frost depth. In warm climates a monolithic slab with a thickened edge is common and cheap. Where the ground freezes deeply, most codes want a separate frost-depth footing under the walls, poured before the slab.

Rebar or wire mesh for a garage floor?

Rebar on a 16 to 18 inch grid is the usual choice for a garage, because the slab carries concentrated wheel loads. Mesh is acceptable on a well-compacted base for light vehicle use, but it has to sit mid-slab to do anything.

How long before I can park on a new garage slab?

Foot traffic after 24 to 48 hours, cars after 7 days, and heavy trucks after 28 days when the concrete reaches full design strength. Parking early is how a new slab picks up its first cracks.

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