Concrete for a 14×18 slab
3.11 cubic yards (154 × 80 lb bags)
for a 14×18 ft slab 4 inches thick: 84 cu ft. Bag counts include 10% extra; at 6 inches you need 4.67 yards.
A 14×18 foot slab covers 252 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 84 cubic feet of concrete, or 3.11 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 3.5 yards, roughly $578 before delivery fees, against $1,001 for 154 bags of 80 lb mix.
Concrete for a 14×18 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 2.33 | 63 | 116 | 154 | 231 |
| 4 in | 3.11 | 84 | 154 | 206 | 308 |
| 5 in | 3.89 | 105 | 193 | 257 | 385 |
| 6 in | 4.67 | 126 | 231 | 308 | 462 |
| 8 in | 6.22 | 168 | 308 | 411 | 616 |
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: 18 × 14 × 0.333 = 84 cu ft.
- Divide by 27 for cubic yards: 84 ÷ 27 = 3.111 cu yd.
- Add 10% and divide by the bag yield: 92.4 ÷ 0.6 = 154 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 3.11 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
- 15×18 slab
- 14×16 slab
- 14×20 slab
- 12×18 slab
- 16×18 slab
- 14×15 slab
- 14×14 slab
- 14×22 slab
- 10×18 slab
- 18×18 slab
- 12×14 slab
- 14×24 slab
Questions
- How many bags of concrete do I need for a 14×18 slab?
- At 4 inches thick, a 14×18 slab takes 154 bags of 80 lb concrete mix, 206 bags of 60 lb mix or 308 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 14×18 slab?
- 3.11 cubic yards at 4 inches thick, 3.89 at 5 inches and 4.67 at 6 inches, before adding extra for waste.
- How much does a 14×18 concrete slab cost?
- The concrete alone for a 4 inch 14×18 slab costs about $1,001 in 154 bags of 80 lb mix (at about $7 a bag) or about $578 for 3.5 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $1,512 to $3,024 for 252 sq ft.
- How much does a 14×18 slab weigh?
- About 6.1 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).