2-inch concrete slab bag chart
| Slab size | 40 lb bags | 50 lb bags | 60 lb bags | 80 lb bags |
|---|---|---|---|---|
| 2 × 2 ft | 3 | 2 | 2 | 2 |
| 3 × 3 ft | 6 | 5 | 4 | 3 |
| 4 × 4 ft | 10 | 8 | 7 | 5 |
| 5 × 5 ft | 16 | 13 | 11 | 8 |
| 6 × 6 ft | 23 | 18 | 15 | 12 |
| 8 × 8 ft | 40 | 32 | 27 | 20 |
| 10 × 10 ft | 62 | 49 | 41 | 31 |
| 10 × 12 ft | 74 | 59 | 49 | 37 |
| 12 × 12 ft | 89 | 71 | 59 | 45 |
4-inch concrete slab bag chart
| Slab size | 40 lb bags | 50 lb bags | 60 lb bags | 80 lb bags |
|---|---|---|---|---|
| 2 × 2 ft | 5 | 4 | 4 | 3 |
| 3 × 3 ft | 12 | 9 | 8 | 6 |
| 4 × 4 ft | 20 | 16 | 14 | 10 |
| 5 × 5 ft | 31 | 25 | 21 | 16 |
| 6 × 6 ft | 45 | 36 | 30 | 23 |
| 8 × 8 ft | 79 | 63 | 53 | 40 |
| 10 × 10 ft | 123 | 98 | 82 | 62 |
| 10 × 12 ft | 147 | 118 | 98 | 74 |
| 12 × 12 ft | 177 | 141 | 118 | 89 |
6-inch concrete slab bag chart
| Slab size | 40 lb bags | 50 lb bags | 60 lb bags | 80 lb bags |
|---|---|---|---|---|
| 2 × 2 ft | 8 | 6 | 5 | 4 |
| 3 × 3 ft | 17 | 14 | 11 | 9 |
| 4 × 4 ft | 30 | 24 | 20 | 15 |
| 5 × 5 ft | 46 | 37 | 31 | 23 |
| 6 × 6 ft | 66 | 53 | 44 | 33 |
| 8 × 8 ft | 118 | 94 | 79 | 59 |
| 10 × 10 ft | 184 | 147 | 123 | 92 |
| 10 × 12 ft | 220 | 176 | 147 | 110 |
| 12 × 12 ft | 264 | 212 | 176 | 132 |
Planning values include 10% extra. Actual bag yield varies by product, mix design, placement and site conditions. Use the yield stated by the manufacturer for purchasing.
How concrete bag quantity is calculated
First calculate the concrete volume: length × width × thickness. Convert thickness from inches to feet, then divide the resulting cubic feet by the bag yield. Add your chosen extra-material allowance and always round up to a whole bag.
Example: 10 × 10 slab at 4 inches thick
A 10 × 10 ft slab at 4 inches thick has about 33.3 cubic feet of net volume. With 10% extra, the planning quantity is about 36.7 cubic feet. At an approximate 0.60 ft³ yield per 80 lb bag, that rounds up to 62 bags.
Calculate your exact concrete project
Enter any length, width, thickness and waste allowance, then compare cubic yards, ready-mix quantity and all four common bag sizes.
Open Concrete Calculator →When should you consider ready-mix instead?
As bag counts become large, handling and mixing individual bags can become impractical. Use the calculator’s cubic-yard and ready-mix order outputs to compare delivery with bagged concrete for your specific project.
For slabs, patios, driveways, footings and post holes, browse the Concrete Planning Hub.