Concrete for a 20×22 slab
5.43 cubic yards (269 × 80 lb bags)
for a 20×22 ft slab 4 inches thick: 146.7 cu ft. Bag counts include 10% extra; at 6 inches you need 8.15 yards.
A 20×22 foot slab covers 440 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 146.7 cubic feet of concrete, or 5.43 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 6 yards, roughly $990 before delivery fees, against $1,749 for 269 bags of 80 lb mix.
Concrete for a 20×22 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 4.07 | 110 | 202 | 269 | 404 |
| 4 in | 5.43 | 146.7 | 269 | 359 | 538 |
| 5 in | 6.79 | 183.3 | 337 | 449 | 673 |
| 6 in | 8.15 | 220 | 404 | 538 | 807 |
| 8 in | 10.86 | 293.3 | 538 | 718 | 1076 |
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: 22 × 20 × 0.333 = 146.67 cu ft.
- Divide by 27 for cubic yards: 146.67 ÷ 27 = 5.432 cu yd.
- Add 10% and divide by the bag yield: 161.33 ÷ 0.6 = 269 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 5.43 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
- 20×20 slab
- 20×24 slab
- 18×22 slab
- 22×22 slab
- 20×25 slab
- 18×20 slab
- 20×26 slab
- 16×22 slab
- 22×24 slab
- 15×22 slab
- 22×25 slab
- 16×20 slab
Questions
- How many bags of concrete do I need for a 20×22 slab?
- At 4 inches thick, a 20×22 slab takes 269 bags of 80 lb concrete mix, 359 bags of 60 lb mix or 538 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 20×22 slab?
- 5.43 cubic yards at 4 inches thick, 6.79 at 5 inches and 8.15 at 6 inches, before adding extra for waste.
- How much does a 20×22 concrete slab cost?
- The concrete alone for a 4 inch 20×22 slab costs about $1,749 in 269 bags of 80 lb mix (at about $7 a bag) or about $990 for 6 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $2,640 to $5,280 for 440 sq ft.
- How much does a 20×22 slab weigh?
- About 10.6 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).