Concrete for a 25×28 slab
8.64 cubic yards (428 × 80 lb bags)
for a 25×28 ft slab 4 inches thick: 233.3 cu ft. Bag counts include 10% extra; at 6 inches you need 12.96 yards.
A 25×28 foot slab covers 700 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 233.3 cubic feet of concrete, or 8.64 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 9.75 yards, roughly $1,609 before delivery fees, against $2,782 for 428 bags of 80 lb mix.
Concrete for a 25×28 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 6.48 | 175 | 321 | 428 | 642 |
| 4 in | 8.64 | 233.3 | 428 | 571 | 856 |
| 5 in | 10.8 | 291.7 | 535 | 713 | 1070 |
| 6 in | 12.96 | 350 | 642 | 856 | 1284 |
| 8 in | 17.28 | 466.7 | 856 | 1141 | 1712 |
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: 28 × 25 × 0.333 = 233.33 cu ft.
- Divide by 27 for cubic yards: 233.33 ÷ 27 = 8.642 cu yd.
- Add 10% and divide by the bag yield: 256.67 ÷ 0.6 = 428 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 8.64 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
- 24×28 slab
- 26×28 slab
- 25×26 slab
- 25×30 slab
- 25×25 slab
- 22×28 slab
- 28×28 slab
- 24×25 slab
- 25×32 slab
- 20×28 slab
- 28×30 slab
- 22×25 slab
Questions
- How many bags of concrete do I need for a 25×28 slab?
- At 4 inches thick, a 25×28 slab takes 428 bags of 80 lb concrete mix, 571 bags of 60 lb mix or 856 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 25×28 slab?
- 8.64 cubic yards at 4 inches thick, 10.8 at 5 inches and 12.96 at 6 inches, before adding extra for waste.
- How much does a 25×28 concrete slab cost?
- The concrete alone for a 4 inch 25×28 slab costs about $2,782 in 428 bags of 80 lb mix (at about $7 a bag) or about $1,609 for 9.75 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $4,200 to $8,400 for 700 sq ft.
- How much does a 25×28 slab weigh?
- About 16.9 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).