Concrete for a 25×25 slab
7.72 cubic yards (382 × 80 lb bags)
for a 25×25 ft slab 4 inches thick: 208.3 cu ft. Bag counts include 10% extra; at 6 inches you need 11.57 yards.
A 25×25 foot slab covers 625 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 208.3 cubic feet of concrete, or 7.72 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 8.5 yards, roughly $1,403 before delivery fees, against $2,483 for 382 bags of 80 lb mix.
Concrete for a 25×25 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 5.79 | 156.3 | 287 | 382 | 573 |
| 4 in | 7.72 | 208.3 | 382 | 510 | 764 |
| 5 in | 9.65 | 260.4 | 478 | 637 | 955 |
| 6 in | 11.57 | 312.5 | 573 | 764 | 1146 |
| 8 in | 15.43 | 416.7 | 764 | 1019 | 1528 |
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: 25 × 25 × 0.333 = 208.33 cu ft.
- Divide by 27 for cubic yards: 208.33 ÷ 27 = 7.716 cu yd.
- Add 10% and divide by the bag yield: 229.17 ÷ 0.6 = 382 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 7.72 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
- 24×25 slab
- 25×26 slab
- 22×25 slab
- 25×28 slab
- 20×25 slab
- 25×30 slab
- 18×25 slab
- 25×32 slab
- 16×25 slab
- 15×25 slab
- 14×25 slab
- 25×36 slab
Questions
- How many bags of concrete do I need for a 25×25 slab?
- At 4 inches thick, a 25×25 slab takes 382 bags of 80 lb concrete mix, 510 bags of 60 lb mix or 764 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 25×25 slab?
- 7.72 cubic yards at 4 inches thick, 9.65 at 5 inches and 11.57 at 6 inches, before adding extra for waste.
- How much does a 25×25 concrete slab cost?
- The concrete alone for a 4 inch 25×25 slab costs about $2,483 in 382 bags of 80 lb mix (at about $7 a bag) or about $1,403 for 8.5 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $3,750 to $7,500 for 625 sq ft.
- How much does a 25×25 slab weigh?
- About 15.1 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).