Concrete for a 14×20 slab
3.46 cubic yards (172 × 80 lb bags)
for a 14×20 ft slab 4 inches thick: 93.3 cu ft. Bag counts include 10% extra; at 6 inches you need 5.19 yards.
A 14×20 foot slab covers 280 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 93.3 cubic feet of concrete, or 3.46 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 4 yards, roughly $660 before delivery fees, against $1,118 for 172 bags of 80 lb mix.
Concrete for a 14×20 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 2.59 | 70 | 129 | 172 | 257 |
| 4 in | 3.46 | 93.3 | 172 | 229 | 343 |
| 5 in | 4.32 | 116.7 | 214 | 286 | 428 |
| 6 in | 5.19 | 140 | 257 | 343 | 514 |
| 8 in | 6.91 | 186.7 | 343 | 457 | 685 |
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: 20 × 14 × 0.333 = 93.33 cu ft.
- Divide by 27 for cubic yards: 93.33 ÷ 27 = 3.457 cu yd.
- Add 10% and divide by the bag yield: 102.67 ÷ 0.6 = 172 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 3.46 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
- 15×20 slab
- 14×18 slab
- 14×22 slab
- 12×20 slab
- 16×20 slab
- 14×16 slab
- 14×24 slab
- 14×15 slab
- 14×25 slab
- 10×20 slab
- 18×20 slab
- 14×14 slab
Questions
- How many bags of concrete do I need for a 14×20 slab?
- At 4 inches thick, a 14×20 slab takes 172 bags of 80 lb concrete mix, 229 bags of 60 lb mix or 343 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 14×20 slab?
- 3.46 cubic yards at 4 inches thick, 4.32 at 5 inches and 5.19 at 6 inches, before adding extra for waste.
- How much does a 14×20 concrete slab cost?
- The concrete alone for a 4 inch 14×20 slab costs about $1,118 in 172 bags of 80 lb mix (at about $7 a bag) or about $660 for 4 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $1,680 to $3,360 for 280 sq ft.
- How much does a 14×20 slab weigh?
- About 6.8 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).