Concrete for a 12×25 slab
3.7 cubic yards (184 × 80 lb bags)
for a 12×25 ft slab 4 inches thick: 100 cu ft. Bag counts include 10% extra; at 6 inches you need 5.56 yards.
A 12×25 foot slab covers 300 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 100 cubic feet of concrete, or 3.7 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 4.25 yards, roughly $701 before delivery fees, against $1,196 for 184 bags of 80 lb mix.
Concrete for a 12×25 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 2.78 | 75 | 138 | 184 | 275 |
| 4 in | 3.7 | 100 | 184 | 245 | 367 |
| 5 in | 4.63 | 125 | 230 | 306 | 459 |
| 6 in | 5.56 | 150 | 275 | 367 | 550 |
| 8 in | 7.41 | 200 | 367 | 489 | 734 |
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 × 12 × 0.333 = 100 cu ft.
- Divide by 27 for cubic yards: 100 ÷ 27 = 3.704 cu yd.
- Add 10% and divide by the bag yield: 110 ÷ 0.6 = 184 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 3.7 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
- 12×24 slab
- 12×26 slab
- 12×22 slab
- 12×28 slab
- 10×25 slab
- 14×25 slab
- 12×20 slab
- 12×30 slab
- 15×25 slab
- 12×18 slab
- 12×32 slab
- 8×25 slab
Questions
- How many bags of concrete do I need for a 12×25 slab?
- At 4 inches thick, a 12×25 slab takes 184 bags of 80 lb concrete mix, 245 bags of 60 lb mix or 367 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 12×25 slab?
- 3.7 cubic yards at 4 inches thick, 4.63 at 5 inches and 5.56 at 6 inches, before adding extra for waste.
- How much does a 12×25 concrete slab cost?
- The concrete alone for a 4 inch 12×25 slab costs about $1,196 in 184 bags of 80 lb mix (at about $7 a bag) or about $701 for 4.25 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $1,800 to $3,600 for 300 sq ft.
- How much does a 12×25 slab weigh?
- About 7.3 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).