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Concrete for a 20 × 20 slab
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4.94 yd³
20 × 20 ft (400 ft²) at 4 in thick, before waste
Concrete for a 20 × 20 slab by thickness
| Thickness | yd³ | yd³ +10% | 80 lb bags | 60 lb bags | Ready-mix @ $165/yd³ |
|---|---|---|---|---|---|
| 4 in | 4.94 | 5.43 | 245 | 326 | $896 |
| 5 in | 6.17 | 6.79 | 306 | 408 | $1,120 |
| 6 in | 7.41 | 8.15 | 367 | 489 | $1,344 |
| 8 in | 9.88 | 10.86 | 489 | 652 | $1,793 |
Bags include 10% extra. Ready-mix prices vary by region; small loads often carry a short-load fee.
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FAQ
How much concrete do I need for a 20x20 slab?
A 20 × 20 ft slab 4 in thick is 4.94 cubic yards; order about 5.43 yd³ with 10% extra. At 6 in thick it is 7.41 yd³.
How many bags of concrete for a 20x20 slab?
About 245 bags of 80 lb concrete (or 326 × 60 lb) at 4 in thick including 10% extra. For this size, ready-mix delivery is usually more practical than bags.
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