Concrete for a 30×32 slab
11.85 cubic yards (587 × 80 lb bags)
for a 30×32 ft slab 4 inches thick: 320 cu ft. Bag counts include 10% extra; at 6 inches you need 17.78 yards.
A 30×32 foot slab covers 960 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 320 cubic feet of concrete, or 11.85 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 13.25 yards, roughly $2,186 before delivery fees, against $3,816 for 587 bags of 80 lb mix.
Concrete for a 30×32 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 8.89 | 240 | 440 | 587 | 880 |
| 4 in | 11.85 | 320 | 587 | 783 | 1174 |
| 5 in | 14.81 | 400 | 734 | 978 | 1467 |
| 6 in | 17.78 | 480 | 880 | 1174 | 1760 |
| 8 in | 23.7 | 640 | 1174 | 1565 | 2347 |
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 × 30 × 0.333 = 320 cu ft.
- Divide by 27 for cubic yards: 320 ÷ 27 = 11.852 cu yd.
- Add 10% and divide by the bag yield: 352 ÷ 0.6 = 587 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 11.85 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
- 30×30 slab
- 28×32 slab
- 32×32 slab
- 28×30 slab
- 30×36 slab
- 26×32 slab
- 25×32 slab
- 26×30 slab
- 24×32 slab
- 32×36 slab
- 25×30 slab
- 24×30 slab
Questions
- How many bags of concrete do I need for a 30×32 slab?
- At 4 inches thick, a 30×32 slab takes 587 bags of 80 lb concrete mix, 783 bags of 60 lb mix or 1174 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 30×32 slab?
- 11.85 cubic yards at 4 inches thick, 14.81 at 5 inches and 17.78 at 6 inches, before adding extra for waste.
- How much does a 30×32 concrete slab cost?
- The concrete alone for a 4 inch 30×32 slab costs about $3,816 in 587 bags of 80 lb mix (at about $7 a bag) or about $2,186 for 13.25 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $5,760 to $11,520 for 960 sq ft.
- How much does a 30×32 slab weigh?
- About 23.2 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).