Concrete for a 28×32 slab
11.06 cubic yards (548 × 80 lb bags)
for a 28×32 ft slab 4 inches thick: 298.7 cu ft. Bag counts include 10% extra; at 6 inches you need 16.59 yards.
A 28×32 foot slab covers 896 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 298.7 cubic feet of concrete, or 11.06 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 12.25 yards, roughly $2,021 before delivery fees, against $3,562 for 548 bags of 80 lb mix.
Concrete for a 28×32 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 8.3 | 224 | 411 | 548 | 822 |
| 4 in | 11.06 | 298.7 | 548 | 731 | 1096 |
| 5 in | 13.83 | 373.3 | 685 | 913 | 1369 |
| 6 in | 16.59 | 448 | 822 | 1096 | 1643 |
| 8 in | 22.12 | 597.3 | 1096 | 1461 | 2191 |
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 × 28 × 0.333 = 298.67 cu ft.
- Divide by 27 for cubic yards: 298.67 ÷ 27 = 11.062 cu yd.
- Add 10% and divide by the bag yield: 328.53 ÷ 0.6 = 548 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 11.06 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
- 28×30 slab
- 26×32 slab
- 30×32 slab
- 25×32 slab
- 28×28 slab
- 28×36 slab
- 24×32 slab
- 32×32 slab
- 26×28 slab
- 22×32 slab
- 25×28 slab
- 24×28 slab
Questions
- How many bags of concrete do I need for a 28×32 slab?
- At 4 inches thick, a 28×32 slab takes 548 bags of 80 lb concrete mix, 731 bags of 60 lb mix or 1096 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 28×32 slab?
- 11.06 cubic yards at 4 inches thick, 13.83 at 5 inches and 16.59 at 6 inches, before adding extra for waste.
- How much does a 28×32 concrete slab cost?
- The concrete alone for a 4 inch 28×32 slab costs about $3,562 in 548 bags of 80 lb mix (at about $7 a bag) or about $2,021 for 12.25 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $5,376 to $10,752 for 896 sq ft.
- How much does a 28×32 slab weigh?
- About 21.7 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).