Concrete for a 6×30 slab
2.22 cubic yards (110 × 80 lb bags)
for a 6×30 ft slab 4 inches thick: 60 cu ft. Bag counts include 10% extra; at 6 inches you need 3.33 yards.
A 6×30 foot slab covers 180 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 60 cubic feet of concrete, or 2.22 cubic yards. At this size you can mix 110 bags of 80 lb (about $715 and a long day of mixing) or order 2.5 yards of ready-mix (about $413, plus the short-load fee most suppliers charge under 3 to 4 yards).
Concrete for a 6×30 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 1.67 | 45 | 83 | 110 | 165 |
| 4 in | 2.22 | 60 | 110 | 147 | 220 |
| 5 in | 2.78 | 75 | 138 | 184 | 275 |
| 6 in | 3.33 | 90 | 165 | 220 | 330 |
| 8 in | 4.44 | 120 | 220 | 294 | 440 |
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: 30 × 6 × 0.333 = 60 cu ft.
- Divide by 27 for cubic yards: 60 ÷ 27 = 2.222 cu yd.
- Add 10% and divide by the bag yield: 66 ÷ 0.6 = 110 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 2.22 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
- 6×28 slab
- 6×32 slab
- 6×26 slab
- 5×30 slab
- 6×25 slab
- 6×24 slab
- 6×36 slab
- 6×22 slab
- 4×30 slab
- 6×20 slab
- 6×40 slab
- 8×30 slab
Questions
- How many bags of concrete do I need for a 6×30 slab?
- At 4 inches thick, a 6×30 slab takes 110 bags of 80 lb concrete mix, 147 bags of 60 lb mix or 220 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 6×30 slab?
- 2.22 cubic yards at 4 inches thick, 2.78 at 5 inches and 3.33 at 6 inches, before adding extra for waste.
- How much does a 6×30 concrete slab cost?
- The concrete alone for a 4 inch 6×30 slab costs about $715 in 110 bags of 80 lb mix (at about $7 a bag) or about $413 for 2.5 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $1,080 to $2,160 for 180 sq ft.
- How much does a 6×30 slab weigh?
- About 4.4 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).