Concrete for a 30×50 slab
18.52 cubic yards (917 × 80 lb bags)
for a 30×50 ft slab 4 inches thick: 500 cu ft. Bag counts include 10% extra; at 6 inches you need 27.78 yards.
A 30×50 foot slab covers 1500 square feet. At the standard 4 inch thickness for a patio, walkway or shed floor, that is 500 cubic feet of concrete, or 18.52 cubic yards. At this size ready-mix is cheaper and far less work than bags: about 20.5 yards, roughly $3,383 before delivery fees, against $5,961 for 917 bags of 80 lb mix.
Concrete for a 30×50 slab by thickness
| Thickness | Cubic yards | Cubic feet | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|---|
| 3 in | 13.89 | 375 | 688 | 917 | 1375 |
| 4 in | 18.52 | 500 | 917 | 1223 | 1834 |
| 5 in | 23.15 | 625 | 1146 | 1528 | 2292 |
| 6 in | 27.78 | 750 | 1375 | 1834 | 2750 |
| 8 in | 37.04 | 1,000 | 1834 | 2445 | 3667 |
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 × 30 × 0.333 = 500 cu ft.
- Divide by 27 for cubic yards: 500 ÷ 27 = 18.519 cu yd.
- Add 10% and divide by the bag yield: 550 ÷ 0.6 = 917 bags of 80 lb mix (rounded up).
Under the slab, plan on 4 inches of compacted gravel: about 18.52 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
- 28×50 slab
- 32×50 slab
- 26×50 slab
- 25×50 slab
- 24×50 slab
- 30×40 slab
- 36×50 slab
- 22×50 slab
- 30×36 slab
- 20×50 slab
- 40×50 slab
- 30×32 slab
Questions
- How many bags of concrete do I need for a 30×50 slab?
- At 4 inches thick, a 30×50 slab takes 917 bags of 80 lb concrete mix, 1223 bags of 60 lb mix or 1834 bags of 40 lb mix, including 10% extra.
- How many yards of concrete for a 30×50 slab?
- 18.52 cubic yards at 4 inches thick, 23.15 at 5 inches and 27.78 at 6 inches, before adding extra for waste.
- How much does a 30×50 concrete slab cost?
- The concrete alone for a 4 inch 30×50 slab costs about $5,961 in 917 bags of 80 lb mix (at about $7 a bag) or about $3,383 for 20.5 yards of ready-mix (at about $165 a yard, before delivery fees). Professionally poured slabs usually run $6 to $12 per square foot, about $9,000 to $18,000 for 1500 sq ft.
- How much does a 30×50 slab weigh?
- About 36.3 tons at 4 inches thick (concrete weighs about 145 lb per cubic foot).