Concrete for a 14×40 slab
6.91 cubic yards (343 × 80 lb bags)
for a 14×40 ft slab 4 inches thick: 186.7 cu ft. Bag counts include 10% extra; at 6 inches you need 10.37 yards.
A 14×40 foot slab covers 560 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 186.7 cubic feet of concrete, or 6.91 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 7.75 yards, roughly $1,279 before delivery fees, against $2,230 for 343 bags of 80 lb mix.
Concrete for a 14×40 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 5.19 | 140 | 257 | 343 | 514 |
| 4 in | 6.91 | 186.7 | 343 | 457 | 685 |
| 5 in | 8.64 | 233.3 | 428 | 571 | 856 |
| 6 in | 10.37 | 280 | 514 | 685 | 1027 |
| 8 in | 13.83 | 373.3 | 685 | 913 | 1369 |
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: 40 × 14 × 0.333 = 186.67 cu ft.
- Divide by 27 for cubic yards: 186.67 ÷ 27 = 6.914 cu yd.
- Add 10% and divide by the bag yield: 205.33 ÷ 0.6 = 343 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 6.91 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
- 15×40 slab
- 14×36 slab
- 12×40 slab
- 16×40 slab
- 14×32 slab
- 14×30 slab
- 14×50 slab
- 10×40 slab
- 18×40 slab
- 14×28 slab
- 14×26 slab
- 14×25 slab
Questions
- How many bags of concrete do I need for a 14×40 slab?
- At 4 inches thick, a 14×40 slab takes 343 bags of 80 lb concrete mix, 457 bags of 60 lb mix or 685 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 14×40 slab?
- 6.91 cubic yards at 4 inches thick, 8.64 at 5 inches and 10.37 at 6 inches, before adding extra for waste.
- How much does a 14×40 concrete slab cost?
- The concrete alone for a 4 inch 14×40 slab costs about $2,230 in 343 bags of 80 lb mix (at about $7 a bag) or about $1,279 for 7.75 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $3,360 to $6,720 for 560 sq ft.
- How much does a 14×40 slab weigh?
- About 13.5 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).