Supply Math
The same chart as a table
| Slab size | 4 in thick | 5 in thick | 6 in thick |
|---|---|---|---|
| 4 × 4 ft | 10 bags · 0.22 yd³ | 13 bags · 0.27 yd³ | 15 bags · 0.33 yd³ |
| 6 × 6 ft | 22 bags · 0.49 yd³ | 28 bags · 0.61 yd³ | 33 bags · 0.73 yd³ |
| 8 × 8 ft | 40 bags · 0.87 yd³ | 49 bags · 1.09 yd³ | 59 bags · 1.3 yd³ |
| 10 × 10 ft | 62 bags · 1.36 yd³ | 77 bags · 1.7 yd³ | 92 bags · 2.04 yd³ |
| 10 × 12 ft | 74 bags · 1.63 yd³ | 92 bags · 2.04 yd³ | 110 bags · 2.44 yd³ |
| 12 × 12 ft | 88 bags · 1.96 yd³ | 110 bags · 2.44 yd³ | 132 bags · 2.93 yd³ |
| 10 × 20 ft | 123 bags · 2.72 yd³ | 153 bags · 3.4 yd³ | 184 bags · 4.07 yd³ |
| 12 × 20 ft | 147 bags · 3.26 yd³ | 184 bags · 4.07 yd³ | 220 bags · 4.89 yd³ |
| 16 × 16 ft | 157 bags · 3.48 yd³ | 196 bags · 4.35 yd³ | 235 bags · 5.21 yd³ |
| 20 × 20 ft | 245 bags · 5.43 yd³ | 306 bags · 6.79 yd³ | 367 bags · 8.15 yd³ |
| 24 × 24 ft | 352 bags · 7.82 yd³ | 440 bags · 9.78 yd³ | 528 bags · 11.73 yd³ |
How this chart is calculated
Volume = length × width × thickness (in feet), plus 10% for waste and uneven ground. Each 80 lb bag makes about 0.60 cubic feet (Quikrete Concrete Mix data sheet), rounded up to whole bags. For any other size, use the concrete calculator; over about 1 cubic yard, compare ready-mix delivery.
Frequently asked questions
How many 80 lb bags of concrete do I need for a 10x10 slab?
About 62 bags for a 4 inch slab, including 10% extra (1.36 cubic yards). At 6 inches it’s about 92 bags.
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