Concrete for a 50×50 slab
30.86 cubic yards (1528 × 80 lb bags)
for a 50×50 ft slab 4 inches thick: 833.3 cu ft. Bag counts include 10% extra; at 6 inches you need 46.3 yards.
A 50×50 foot slab covers 2500 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 833.3 cubic feet of concrete, or 30.86 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 34 yards, roughly $5,610 before delivery fees, against $9,932 for 1528 bags of 80 lb mix.
Concrete for a 50×50 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 23.15 | 625 | 1146 | 1528 | 2292 |
| 4 in | 30.86 | 833.3 | 1528 | 2038 | 3056 |
| 5 in | 38.58 | 1,041.7 | 1910 | 2547 | 3820 |
| 6 in | 46.3 | 1,250 | 2292 | 3056 | 4584 |
| 8 in | 61.73 | 1,666.7 | 3056 | 4075 | 6112 |
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: 50 × 50 × 0.333 = 833.33 cu ft.
- Divide by 27 for cubic yards: 833.33 ÷ 27 = 30.864 cu yd.
- Add 10% and divide by the bag yield: 916.67 ÷ 0.6 = 1528 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 30.86 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
- 40×50 slab
- 36×50 slab
- 32×50 slab
- 30×50 slab
- 28×50 slab
- 26×50 slab
- 25×50 slab
- 24×50 slab
- 22×50 slab
- 20×50 slab
- 18×50 slab
- 16×50 slab
Questions
- How many bags of concrete do I need for a 50×50 slab?
- At 4 inches thick, a 50×50 slab takes 1528 bags of 80 lb concrete mix, 2038 bags of 60 lb mix or 3056 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 50×50 slab?
- 30.86 cubic yards at 4 inches thick, 38.58 at 5 inches and 46.3 at 6 inches, before adding extra for waste.
- How much does a 50×50 concrete slab cost?
- The concrete alone for a 4 inch 50×50 slab costs about $9,932 in 1528 bags of 80 lb mix (at about $7 a bag) or about $5,610 for 34 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $15,000 to $30,000 for 2500 sq ft.
- How much does a 50×50 slab weigh?
- About 60.4 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).