Concrete Calculator
Estimate concrete volume in cubic feet, cubic yards, and number of bags.
How this calculator works
How to use this calculator
Enter the concrete area length and width in feet, then enter the slab depth in inches or feet. Optionally enter the bag yield to estimate how many concrete bags are needed.
Formula used
Concrete Volume = Length × Width × Depth. Cubic Yards = Cubic Feet ÷ 27. Bags Needed = Cubic Feet ÷ Bag Yield, rounded up.
Example calculation
A 10 ft by 8 ft slab that is 4 inches thick needs 26.67 cubic feet, or 0.988 cubic yards. If each bag yields 0.6 cubic feet, you need 45 bags.
What the result means
The result estimates the volume of concrete needed for a rectangular slab or area.
Frequently asked questions
Why divide by 27 for cubic yards?
One cubic yard contains 27 cubic feet.
Should I order extra concrete?
Many projects include a small extra allowance for uneven ground, spillage, and measurement differences.
Does this work for round holes?
This calculator is for rectangular areas. A circular post-hole calculator would use a different formula.