Concrete for a 18×26 slab
5.78 cubic yards (286 × 80 lb bags)
for a 18×26 ft slab 4 inches thick: 156 cu ft. Bag counts include 10% extra; at 6 inches you need 8.67 yards.
A 18×26 foot slab covers 468 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 156 cubic feet of concrete, or 5.78 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 6.5 yards, roughly $1,073 before delivery fees, against $1,859 for 286 bags of 80 lb mix.
Concrete for a 18×26 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 4.33 | 117 | 215 | 286 | 429 |
| 4 in | 5.78 | 156 | 286 | 382 | 572 |
| 5 in | 7.22 | 195 | 358 | 477 | 715 |
| 6 in | 8.67 | 234 | 429 | 572 | 858 |
| 8 in | 11.56 | 312 | 572 | 763 | 1144 |
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: 26 × 18 × 0.333 = 156 cu ft.
- Divide by 27 for cubic yards: 156 ÷ 27 = 5.778 cu yd.
- Add 10% and divide by the bag yield: 171.6 ÷ 0.6 = 286 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 5.78 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
- 18×25 slab
- 18×24 slab
- 18×28 slab
- 16×26 slab
- 20×26 slab
- 18×22 slab
- 18×30 slab
- 15×26 slab
- 14×26 slab
- 22×26 slab
- 18×20 slab
- 18×32 slab
Questions
- How many bags of concrete do I need for a 18×26 slab?
- At 4 inches thick, a 18×26 slab takes 286 bags of 80 lb concrete mix, 382 bags of 60 lb mix or 572 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 18×26 slab?
- 5.78 cubic yards at 4 inches thick, 7.22 at 5 inches and 8.67 at 6 inches, before adding extra for waste.
- How much does a 18×26 concrete slab cost?
- The concrete alone for a 4 inch 18×26 slab costs about $1,859 in 286 bags of 80 lb mix (at about $7 a bag) or about $1,073 for 6.5 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $2,808 to $5,616 for 468 sq ft.
- How much does a 18×26 slab weigh?
- About 11.3 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).