12x24 Concrete Slab, 4 Inches Thick
A 12 × 24 ft slab (288 sq ft) at 4 in thick takes about 3.91 cubic yards of concrete, with 10% extra for waste. For ready-mix, order 4 cu yd for the 12x24, about $620 – $830 delivered, short-load fee included. Bagged, the same 12x24 is 176 80 lb or 235 60 lb bags, about $1,175 – $1,645 for the concrete alone.
- Ready-mix order
- 4 cu yd
- Ready-mix cost
- $620 – $830
- 80 lb bags
- 176
- Bag cost
- $1,175 – $1,645
The 12x24 (4 in) prices are national material ranges as of 2026-09, not a quote from a supplier.
What a 12x24 slab gives you
A 12x24 is the one-car garage with room to spare: a car plus a workbench or storage shelves across the back, or a car plus a lawn tractor.
The same slab is common under a long carport for a pickup, a single-wide RV pad for a small trailer, or a garden building split into a shed and a potting room.
Twenty-four feet is a standard truss-building length, so many garage kits and pole-building packages come in exactly this size.
A 4 in 12x24 pour: check first
- Mark where the garage door goes so you can form a clean, square threshold.
- Set anchor bolts for the wall plates at the spacing your plans call for while the concrete is wet.
- Leave a drain path at the door end so meltwater from a parked car runs out.
Full plan for a 12x24 slab, 4 in
- Area
- 288 sq ft
- Thickness
- 4 in
- Volume
- 3.91 cu yd
Bagged concrete estimate (DIY)
$1,454 – $2,099
Est. as of 2026-09 — not a live quote
Ready-mix delivered, incl. short-load fee (materials only)
$620 – $830
Est. as of 2026-09 — not a live quote
For a pour this size, ready-mix delivery is typically more practical than mixing bags by hand.
Shopping list
- Concrete mix (60 lb bags) Or 352 × 40 lb, 282 × 50 lb or 176 × 80 lb bags. 235 bags
- Ready-mix concrete Alternative to bagged mix; most suppliers have a 1 cu yd order minimum. 4 cu yd
- Compactable gravel sub-base 4 in compacted base beneath the slab. 4.8 tons
- 6x6 welded wire mesh Reinforcement for crack control; not a substitute for engineered rebar on structural slabs. 317 sq ft
Email me this plan
Get the shopping list, cost range and next steps in your inbox, to have at the store or when you talk to a contractor. Free.
You need about 4 cubic yards of ready-mix concrete. Want local delivered prices?
Get delivered pricesFree · no obligation · any prices come from local suppliers, not us.
Buy bagged concrete
Pick up bagged mix and reinforcement from a hardware store for smaller pours.
View shopping listAssumptions
- Waste allowance: 10% applied to account for over-excavation and spillage.
- Approx. wet weight: 15,840 lb (7.9 tons).
- Prices are national-average retail/delivery ranges as of 2026-09, not live quotes.
- Ready-mix orders under 10 cu yd usually carry a short-load fee; the ready-mix range includes a flat $60-$110. Some suppliers charge per yard instead, so ask for the full fee schedule.
Bags or ready-mix for a 12x24 slab, 4 in?
3.91 cu yd for the 12x24 fits on one ready-mix truck (they carry about 8 to 10 cu yd). In bags the 12x24 would be 176 80 lb bags weighing 14,080 lb, so ready-mix is the practical choice. Under 10 cu yd most suppliers add a short-load fee, and the $620 – $830 range for the 12x24 includes one. Ready-mix wins for this 12x24 by roughly $685 (range midpoints), and nobody has to mix 176 bags by hand.
Is 4 in thick enough for a 12x24 slab?
For a 12x24 garage or shop floor that carries passenger cars, 4 in is common and above the IRC minimum of 3-1/2 in. Go to 5 or 6 in if the 12x24 will hold heavy pickups, an RV, a car lift or a tractor, or sits on soft or clay soil, and check your local code first. At 6 in the same 12x24 takes about 5.87 cu yd.
Control joints for a 12x24 slab at 4 in
A 12x24 slab at 4 in shrinks as it cures, and without joints it cracks wherever it chooses. ACI and PCA guidance spaces joints 24 to 36 times the thickness, which for this 12x24 at 4 in is every 8 to 12 ft, sawn 1 in deep (a quarter of the slab) once the surface holds up to the blade, usually within a day.
On the 12x24 at 4 in, a joint every 10 ft or less means 2 joints across the 24 ft side and 1 joint across the 12 ft side: 6 panels of about 8 × 6 ft and 48 ft of saw cut. The 12x24 is 2 times as long as it is wide, and long, narrow slabs crack across their width, so don't skip its cross joints.
How much a 12x24 slab 4 in thick weighs
Wet concrete weighs about 150 lb per cubic foot, so the 12x24 pour is about 15,840 lb (7.9 tons). As bags, the 12x24 is 176 80 lb bags, 14,080 lb in all: about 10 trips in a pickup carrying 1,500 lb a load. Nobody hauls 14,080 lb of bags for a 12x24 in a pickup; it comes by ready-mix truck or as pallets on a delivery truck.
The 12x24 at 4 in against nearby sizes
Every row uses the same 10% waste and prices as the 12x24 at 4 in; costs are for the concrete only.
| Slab | Cu yd | 60 lb bags | 80 lb bags | Ready-mix order | Bags cost | Ready-mix cost |
|---|---|---|---|---|---|---|
| 16x16 slab, 4 in | 3.48 | 209 | 157 | 3.5 cu yd | $1,045 – $1,463 | $550 – $740 |
| 12x24 slab, 4 in (this page) | 3.91 | 235 | 176 | 4 cu yd | $1,175 – $1,645 | $620 – $830 |
| 16x20 slab, 4 in | 4.35 | 261 | 196 | 4.5 cu yd | $1,305 – $1,827 | $690 – $920 |
Questions about a 12x24 slab, 4 in
How many bags of concrete for a 12x24 slab 4 inches thick?
Plan on 105.6 cubic feet for the 12x24, which is 176 80 lb bags, 235 60 lb bags, 282 50 lb or 352 40 lb bags once 10% waste is in.
How many yards of concrete for a 12x24 slab 4 inches thick?
3.91 cubic yards with waste (3.56 without) for a 12x24 at 4 in. Round the 12x24 order to 4 cu yd: plants batch in quarter yards and most won't send less than a yard.
How much does a 12x24 concrete slab 4 inches thick cost?
Concrete alone for the 12x24 runs about $620 – $830 for 4 cu yd of ready-mix delivered, short-load fee included, or $1,175 – $1,645 for 235 60 lb bags. Add a 4 in gravel base and wire mesh and the bagged 12x24 plan comes to $1,454 – $2,099. Labor, forms and finishing for a 12x24 at 4 in come on top of these national ranges (as of 2026-09), which are not quotes.
How much does a 12x24 concrete slab 4 inches thick weigh?
About 15,840 lb (7.9 tons) of wet concrete for the 12x24, at 150 lb per cubic foot. The 176 80 lb bags for a 12x24 weigh 14,080 lb: about 10 trips in a pickup carrying 1,500 lb a load.
Where do control joints go on a 12x24 slab 4 inches thick?
On a 12x24 at 4 in, every 8 to 12 ft (24 to 36 times the thickness), sawn 1 in deep. On the 12x24 at 4 in, a joint every 10 ft or less means 2 joints across the 24 ft side and 1 joint across the 12 ft side: 6 panels of about 8 × 6 ft and 48 ft of saw cut.
Limitations
The 12x24 figures at 4 in are material estimates and typical price ranges, not a quote or a structural design. Confirm that 4 in, the reinforcement and the joint layout suit your soil, loads and local code for a 12x24 slab with a qualified professional.