Concrete for a 25×30 slab
9.26 cubic yards (459 × 80 lb bags)
for a 25×30 ft slab 4 inches thick: 250 cu ft. Bag counts include 10% extra; at 6 inches you need 13.89 yards.
A 25×30 foot slab covers 750 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 250 cubic feet of concrete, or 9.26 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 10.25 yards, roughly $1,691 before delivery fees, against $2,984 for 459 bags of 80 lb mix.
Concrete for a 25×30 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 6.94 | 187.5 | 344 | 459 | 688 |
| 4 in | 9.26 | 250 | 459 | 612 | 917 |
| 5 in | 11.57 | 312.5 | 573 | 764 | 1146 |
| 6 in | 13.89 | 375 | 688 | 917 | 1375 |
| 8 in | 18.52 | 500 | 917 | 1223 | 1834 |
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: 30 × 25 × 0.333 = 250 cu ft.
- Divide by 27 for cubic yards: 250 ÷ 27 = 9.259 cu yd.
- Add 10% and divide by the bag yield: 275 ÷ 0.6 = 459 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 9.26 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
- 24×30 slab
- 26×30 slab
- 25×28 slab
- 25×32 slab
- 22×30 slab
- 28×30 slab
- 25×26 slab
- 25×25 slab
- 20×30 slab
- 24×25 slab
- 25×36 slab
- 30×30 slab
Questions
- How many bags of concrete do I need for a 25×30 slab?
- At 4 inches thick, a 25×30 slab takes 459 bags of 80 lb concrete mix, 612 bags of 60 lb mix or 917 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 25×30 slab?
- 9.26 cubic yards at 4 inches thick, 11.57 at 5 inches and 13.89 at 6 inches, before adding extra for waste.
- How much does a 25×30 concrete slab cost?
- The concrete alone for a 4 inch 25×30 slab costs about $2,984 in 459 bags of 80 lb mix (at about $7 a bag) or about $1,691 for 10.25 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $4,500 to $9,000 for 750 sq ft.
- How much does a 25×30 slab weigh?
- About 18.1 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).