A 24x24 slab poured 4 inches thick needs 7.11 cubic yards of concrete (192 cubic feet: 24 ft × 24 ft × 4 in ÷ 12). With 10 percent extra you order 8 cubic yards of ready-mix, or buy 352 bags of 80 lb mix and mix it yourself.
A 24x24 slab is a standard two-car garage footprint at 576 square feet, with room for a workbench along one wall.
How much concrete for a 24x24 slab, by thickness
Volume is the area times the thickness in feet. The 24x24 slab covers 576 sq ft. Ordered volumes include 10 percent extra for uneven sub-base and spillage, the middle of the 4 to 10 percent NRMCA range, and ready-mix is sold in quarter yards.
| Build | Concrete, net | Order with 10% extra | Trucks | Weight |
|---|---|---|---|---|
| 4 in, plain | 7.11 cu yd (192 cu ft) | 8 cu yd | 1 (short load) | 29,568 lb |
| 4 in, wire mesh | 7.11 cu yd (192 cu ft) | 8 cu yd | 1 (short load) | 29,568 lb |
| 6 in, rebar | 10.67 cu yd (288 cu ft) | 11.75 cu yd | 2 | 44,352 lb |
The weight uses 140 lb per cubic foot, Quikrete's figure for the mix. A 6 inch slab is half again the concrete of a 4 inch one for the same footprint, which is worth spending on where a car or a hot tub will sit and not on a walkway.
How many bags of concrete for a 24x24 slab
Bag counts come from the yields on the manufacturers' data sheets: an 80 lb bag makes 0.60 cu ft, 60 lb 0.45, 50 lb 0.375 and 40 lb 0.30. They include the 10 percent allowance.
| Bag size | 4 in slab | 6 in slab |
|---|---|---|
| 80 lb | 352 bags | 528 bags |
| 60 lb | 470 bags | 704 bags |
| 50 lb | 564 bags | 845 bags |
| 40 lb | 704 bags | 1056 bags |
352 bags of 80 lb is 14.1 tons of bagged mix to move and mix by hand, and a slab has to be poured before the first batch stiffens. Ready-mix is the practical route at this size. The concrete bag calculator converts any bag size and brand.
24x24 slab cost, three builds
Installed prices at US averages: ready-mix $110 to $150 per cu yd, delivery, fuel and a short-load fee below a full truck, placing and finishing $2 to $3 per sq ft (HomeAdvisor, June 2026), wire mesh $0.83 to $0.98 per sq ft (homewyse, September 2026) and rebar $2 to $3 per sq ft (This Old House, March 2026).
| Build | Materials only | Installed range | Typical per sq ft | Crew days |
|---|---|---|---|---|
| 4 in, plain | $1,300 to $1,800 | $2,450 to $3,500 (typical $2,950) | $5 | 1.5 |
| 4 in, wire mesh | $1,750 to $2,350 | $2,900 to $4,100 (typical $3,500) | $6 | 1.5 |
| 6 in, rebar | $2,650 to $3,800 | $3,800 to $5,500 (typical $4,700) | $8 | 1.5 |
A 8 cu yd order is well below the 8 to 12 yards a truck carries, so the estimate includes a short-load fee of about $400 ($320 to $480). Splitting a truck with a neighbor who is also pouring avoids it. The heavy build adds 49 bars of 20 ft No. 4 rebar in an 18 in grid, about 655 lb with laps and 10 percent spare; the rebar calculator lays out the grid.
Joints, thickness and permit
The 2024 IRC sets 3½ in as the minimum for a slab on ground (R506.1) over 4 in of granular base with a vapor retarder under floors. NRMCA advises control joints no farther apart than 24 times the thickness: 8 ft for a 4 in slab, 12 ft for a 6 in slab. On a 24x24 slab that means 2 joints each way at 4 in thick. Under IRC 2024 R105.2, sidewalks and driveways need no permit, and a free-standing patio slab is usually treated the same way. A slab that carries a building, such as a 24x24 garage or shed floor, is part of that building's permit.
Forming, placing and finishing is about 1.5 days for a two-person crew. Concrete reaches 2,500 psi at 7 days and 4,000 psi at 28 days (Quikrete data sheet), so keep vehicles off for the first week.
24x24 slab compared with other sizes
A 20x20 slab saves 2.17 cu yd less, $890 less installed. A 30x40 slab needs 7.7 cu yd more, $2,700 more installed.
Next steps for a 24x24 slab
- Change thickness, shape or add a thickened edge in the concrete slab calculator.
- Work out the rebar for the slab at your own spacing.
- Turn the yards into a truck order with the concrete yard calculator, and add pumping or finishes in the concrete cost calculator.
- Any other shape or a footing is in the concrete calculator. All size pages are grouped under cost calculators.