Concrete Calculator
How much concrete do I need?
Enter your slab's length, width and thickness. We show the cubic yards for a ready-mix order and the bags for mixing it yourself, both with 10% extra.
- Or 80 lb bags
- 62 bags
- Or 60 lb bags
- 82 bags
- Exact volume
- 1.23 cubic yards
An estimate to plan and budget with. Measure carefully and check the product’s own figures before you buy.
Results update as you type.
How it’s calculated
- 1
Volume is length × width × thickness (in inches ÷ 12), in cubic feet; ÷ 27 gives cubic yards.
- 2
We add 10% for uneven ground and spillage.
- 3
An 80 lb bag makes about 0.6 cubic feet and a 60 lb bag about 0.45 cubic feet of concrete.
Before you buy
Above about 1 cubic yard (roughly 45 eighty-pound bags), ready-mix delivery is usually easier and more consistent.
Compact a gravel base under the slab and add control joints to guide cracking.
Ask about minimum-order fees: many suppliers charge extra for small loads.
Questions
How many bags of concrete make a yard?
About 45 eighty-pound bags or 60 sixty-pound bags make one cubic yard.
How thick should a concrete slab be?
4 inches for patios and walkways, 5 inches for garage floors, and 6 inches for driveways or heavy loads.