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Concrete Calculator
Calculate how much concrete you need for slabs, walls, columns, holes, curbs and gutters.
About the Concrete Calculator
Calculate how much concrete you need for slabs, walls, columns, holes, curbs and gutters.
How to use the Concrete Calculator
- Choose the shape: Slab / Wall, Column / Hole or Curb / Gutter.
- Enter the dimensions shown.
- Press Calculate Volume.
Formula and method
Slab volume = length × width × thickness. 27 cubic feet = 1 cubic yard.
Worked example
A 10 ft × 10 ft slab that is 4 inches thick has 33.3 cubic feet, or 1.23 cubic yards.
When to use the Concrete Calculator
- Ordering the right amount of concrete for a slab, footing or post holes.
- Comparing bags with a ready-mix delivery.
- Budgeting a patio, driveway or shed base.
Common mistakes to avoid
- Forgetting to convert thickness in inches to feet.
- Ordering exactly the calculated amount, with nothing extra for spillage and uneven ground.
Tips
- Order about 5% to 10% extra for spillage and uneven ground.
Frequently asked questions
How do I convert cubic feet to cubic yards?
Divide by 27.
How many 80 lb bags make one cubic yard?
About 50 bags, since a cubic yard of concrete weighs roughly 4,000 lb.