Concrete for a 4×32 slab
1.58 cubic yards (79 × 80 lb bags)
for a 4×32 ft slab 4 inches thick: 42.7 cu ft. Bag counts include 10% extra; at 6 inches you need 2.37 yards.
A 4×32 foot slab covers 128 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 42.7 cubic feet of concrete, or 1.58 cubic yards. At this size you can mix 79 bags of 80 lb (about $514 and a long day of mixing) or order 1.75 yards of ready-mix (about $289, plus the short-load fee most suppliers charge under 3 to 4 yards).
Concrete for a 4×32 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 1.19 | 32 | 59 | 79 | 118 |
| 4 in | 1.58 | 42.7 | 79 | 105 | 157 |
| 5 in | 1.98 | 53.3 | 98 | 131 | 196 |
| 6 in | 2.37 | 64 | 118 | 157 | 235 |
| 8 in | 3.16 | 85.3 | 157 | 209 | 313 |
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 × 4 × 0.333 = 42.67 cu ft.
- Divide by 27 for cubic yards: 42.67 ÷ 27 = 1.58 cu yd.
- Add 10% and divide by the bag yield: 46.93 ÷ 0.6 = 79 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 1.58 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
- 4×30 slab
- 4×28 slab
- 4×36 slab
- 4×26 slab
- 4×25 slab
- 3×32 slab
- 4×24 slab
- 4×40 slab
- 5×32 slab
- 4×22 slab
- 4×20 slab
- 4×18 slab
Questions
- How many bags of concrete do I need for a 4×32 slab?
- At 4 inches thick, a 4×32 slab takes 79 bags of 80 lb concrete mix, 105 bags of 60 lb mix or 157 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 4×32 slab?
- 1.58 cubic yards at 4 inches thick, 1.98 at 5 inches and 2.37 at 6 inches, before adding extra for waste.
- How much does a 4×32 concrete slab cost?
- The concrete alone for a 4 inch 4×32 slab costs about $514 in 79 bags of 80 lb mix (at about $7 a bag) or about $289 for 1.75 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $768 to $1,536 for 128 sq ft.
- How much does a 4×32 slab weigh?
- About 3.1 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).