Concrete for a 12×32 slab
4.74 cubic yards (235 × 80 lb bags)
for a 12×32 ft slab 4 inches thick: 128 cu ft. Bag counts include 10% extra; at 6 inches you need 7.11 yards.
A 12×32 foot slab covers 384 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 128 cubic feet of concrete, or 4.74 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 5.25 yards, roughly $866 before delivery fees, against $1,528 for 235 bags of 80 lb mix.
Concrete for a 12×32 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 3.56 | 96 | 176 | 235 | 352 |
| 4 in | 4.74 | 128 | 235 | 313 | 470 |
| 5 in | 5.93 | 160 | 294 | 392 | 587 |
| 6 in | 7.11 | 192 | 352 | 470 | 704 |
| 8 in | 9.48 | 256 | 470 | 626 | 939 |
Bag counts include 10% extra for spillage and uneven ground. Cubic yards and cubic feet are the exact volume.
How it’s worked out
- Convert the thickness to feet: 4 in ÷ 12 = 0.333 ft.
- Multiply length × width × thickness: 32 × 12 × 0.333 = 128 cu ft.
- Divide by 27 for cubic yards: 128 ÷ 27 = 4.741 cu yd.
- Add 10% and divide by the bag yield: 140.8 ÷ 0.6 = 235 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 4.74 cubic yards. For driveways and anything that carries a vehicle, go to 5 or 6 inches and add rebar or wire mesh.
Change the numbers
Other slab sizes
- 12×30 slab
- 12×28 slab
- 12×36 slab
- 10×32 slab
- 14×32 slab
- 12×26 slab
- 12×25 slab
- 12×24 slab
- 12×40 slab
- 15×32 slab
- 12×22 slab
- 8×32 slab
Questions
- How many bags of concrete do I need for a 12×32 slab?
- At 4 inches thick, a 12×32 slab takes 235 bags of 80 lb concrete mix, 313 bags of 60 lb mix or 470 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 12×32 slab?
- 4.74 cubic yards at 4 inches thick, 5.93 at 5 inches and 7.11 at 6 inches, before adding extra for waste.
- How much does a 12×32 concrete slab cost?
- The concrete alone for a 4 inch 12×32 slab costs about $1,528 in 235 bags of 80 lb mix (at about $7 a bag) or about $866 for 5.25 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $2,304 to $4,608 for 384 sq ft.
- How much does a 12×32 slab weigh?
- About 9.3 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).