Concrete calculator
Enter the size of the slab, footing or hole. Jobmath gives cubic yards for a truck or the number of bags.
How it's calculated
Each step, in the order Jobmath runs it.
| Step | Formula |
|---|---|
| Slab volume | Length × width × thickness ÷ 12 = cubic feet |
| Column volume | π × (diameter ÷ 24)² × height = cubic feet |
| Cubic yards | Cubic feet ÷ 27 |
| Waste | Volume × (1 + waste %) |
| Bags | Cubic feet ÷ bag yield, rounded up |
Bags per cubic yard
Yields as Quikrete lists them for its premixed concrete.
| Bag | Yield per bag | Bags per cubic yard |
|---|---|---|
| 80 lb | 0.60 cu ft | 45 |
| 60 lb | 0.45 cu ft | 60 |
| 50 lb | 0.375 cu ft | 72 |
| 40 lb | 0.30 cu ft | 90 |