Concrete for a 15×24 slab
4.44 cubic yards (220 × 80 lb bags)
for a 15×24 ft slab 4 inches thick: 120 cu ft. Bag counts include 10% extra; at 6 inches you need 6.67 yards.
A 15×24 foot slab covers 360 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 120 cubic feet of concrete, or 4.44 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 5 yards, roughly $825 before delivery fees, against $1,430 for 220 bags of 80 lb mix.
Concrete for a 15×24 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 3.33 | 90 | 165 | 220 | 330 |
| 4 in | 4.44 | 120 | 220 | 294 | 440 |
| 5 in | 5.56 | 150 | 275 | 367 | 550 |
| 6 in | 6.67 | 180 | 330 | 440 | 660 |
| 8 in | 8.89 | 240 | 440 | 587 | 880 |
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: 24 × 15 × 0.333 = 120 cu ft.
- Divide by 27 for cubic yards: 120 ÷ 27 = 4.444 cu yd.
- Add 10% and divide by the bag yield: 132 ÷ 0.6 = 220 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 4.44 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
- 15×25 slab
- 14×24 slab
- 16×24 slab
- 15×22 slab
- 15×26 slab
- 15×20 slab
- 15×28 slab
- 12×24 slab
- 18×24 slab
- 15×18 slab
- 15×30 slab
- 10×24 slab
Questions
- How many bags of concrete do I need for a 15×24 slab?
- At 4 inches thick, a 15×24 slab takes 220 bags of 80 lb concrete mix, 294 bags of 60 lb mix or 440 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 15×24 slab?
- 4.44 cubic yards at 4 inches thick, 5.56 at 5 inches and 6.67 at 6 inches, before adding extra for waste.
- How much does a 15×24 concrete slab cost?
- The concrete alone for a 4 inch 15×24 slab costs about $1,430 in 220 bags of 80 lb mix (at about $7 a bag) or about $825 for 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 $2,160 to $4,320 for 360 sq ft.
- How much does a 15×24 slab weigh?
- About 8.7 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).