How to calculate concrete for a slab
Enter the length and width in feet (or meters) and the depth in inches (or centimeters). The calculator converts to cubic yards and cubic meters and estimates how many pre-mixed bags you need.
Concrete volume reference
1 cubic yard = 27 cubic feet = 0.765 m3. A 60 lb bag covers about 0.45 cu ft; an 80 lb bag covers 0.60 cu ft. Add 10% extra for waste.
Frequently Asked Questions
Do I need to add extra concrete for waste?
Yes, it is standard practice to order 5-10% more concrete than calculated to account for spillage and uneven surfaces.
Can I use this for cylinders or footings?
This calculator is optimised for rectangular slabs. For cylinders use pi x r2 x height to find the volume in cubic feet, then divide by 27.