How Much Concrete Do I Need for a 8x8 Slab?
For a 8x8 ft slab, 4 in thick, you need about 0.87 yd³ (cubic yards to order (+10% waste)). Also: cubic yards (exact): 0.79 yd³; cubic feet: 21.3 ft³; 80-lb bags of concrete mix: 40 bags.
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| Cubic yards (exact) | 0.79 yd³ |
|---|---|
| Cubic feet | 21.3 ft³ |
| 80-lb bags of concrete mix | 40 bags |
| 60-lb bags of concrete mix | 53 bags |
How this number is calculated
8 ft × 8 ft × 4 in ÷ 12 = 21.3 cubic feet. Divide by 27 to get 0.79 cubic yards, then add 10% for spillage and uneven ground: 0.87 cubic yards.
Nearby sizes
| Size | Cubic yards to order (+10% waste) |
|---|---|
| a 6x6 ft slab, 4 in thick | 0.49 yd³ |
| a 10x10 ft slab, 4 in thick | 1.36 yd³ |
| a 5x5 ft slab, 4 in thick | 0.34 yd³ |
| a 4x4 ft slab, 4 in thick | 0.22 yd³ |
Tips
- Compact the gravel base first. Thickness is measured from the top of the base, not the dirt.
- Order 5–10% extra: a slightly uneven subgrade can swallow more concrete than the math says.
- Ready-mix is cheaper per yard than bagged mix once you need roughly 1 cubic yard or more; below that, bags are easier.
Frequently asked questions
How much concrete do I need for a 8x8 ft slab, 4 in thick?
For a 8x8 ft slab, 4 in thick, you need about 0.87 yd³ (cubic yards to order (+10% waste)). Also: cubic yards (exact): 0.79 yd³; cubic feet: 21.3 ft³; 80-lb bags of concrete mix: 40 bags.
How is the quantity for a 8x8 ft slab, 4 in thick calculated?
8 ft × 8 ft × 4 in ÷ 12 = 21.3 cubic feet. Divide by 27 to get 0.79 cubic yards, then add 10% for spillage and uneven ground: 0.87 cubic yards.
How much does concrete for a 8x8 ft slab, 4 in thick cost?
Using rough planning prices (per cubic yard, ready-mix delivered (small loads can add a short-load fee)), the material for a 8x8 ft slab, 4 in thick comes to about $122 to $174. Prices vary by region and supplier, so get a local quote.