Concrete for a 20×26 slab
6.42 cubic yards (318 × 80 lb bags)
for a 20×26 ft slab 4 inches thick: 173.3 cu ft. Bag counts include 10% extra; at 6 inches you need 9.63 yards.
A 20×26 foot slab covers 520 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 173.3 cubic feet of concrete, or 6.42 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 7.25 yards, roughly $1,196 before delivery fees, against $2,067 for 318 bags of 80 lb mix.
Concrete for a 20×26 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 4.81 | 130 | 239 | 318 | 477 |
| 4 in | 6.42 | 173.3 | 318 | 424 | 636 |
| 5 in | 8.02 | 216.7 | 398 | 530 | 795 |
| 6 in | 9.63 | 260 | 477 | 636 | 954 |
| 8 in | 12.84 | 346.7 | 636 | 848 | 1272 |
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 × 20 × 0.333 = 173.33 cu ft.
- Divide by 27 for cubic yards: 173.33 ÷ 27 = 6.42 cu yd.
- Add 10% and divide by the bag yield: 190.67 ÷ 0.6 = 318 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 6.42 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
- 20×25 slab
- 20×24 slab
- 20×28 slab
- 18×26 slab
- 22×26 slab
- 20×22 slab
- 20×30 slab
- 16×26 slab
- 24×26 slab
- 20×20 slab
- 20×32 slab
- 15×26 slab
Questions
- How many bags of concrete do I need for a 20×26 slab?
- At 4 inches thick, a 20×26 slab takes 318 bags of 80 lb concrete mix, 424 bags of 60 lb mix or 636 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 20×26 slab?
- 6.42 cubic yards at 4 inches thick, 8.02 at 5 inches and 9.63 at 6 inches, before adding extra for waste.
- How much does a 20×26 concrete slab cost?
- The concrete alone for a 4 inch 20×26 slab costs about $2,067 in 318 bags of 80 lb mix (at about $7 a bag) or about $1,196 for 7.25 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $3,120 to $6,240 for 520 sq ft.
- How much does a 20×26 slab weigh?
- About 12.6 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).