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Concrete Calculator
Calculate how much concrete you need for a rectangular slab or project using length, width, depth, and a waste allowance.
How to Use the Concrete Calculator
Enter the length, width, and depth of your project. You can choose different units for each measurement, including feet, inches, yards, meters, and centimeters.
The calculator converts the measurements and estimates the volume of concrete needed in cubic feet and cubic yards. You can also include a waste allowance to account for spills, uneven surfaces, and other material loss.
How Much Concrete Do I Need?
The amount of concrete required depends on the length, width, and thickness of the area you are filling.
For a rectangular project, the basic volume formula is:
Volume = Length × Width × Depth
When measurements are in feet, the result is cubic feet. To convert cubic feet to cubic yards, divide the volume by 27.
Adding a Waste Allowance
It is common to order some additional concrete beyond the calculated volume. This provides a margin for measurement differences, uneven ground, spills, and other unexpected material requirements.
The calculator lets you enter a waste allowance percentage. The additional amount is then included in the estimated concrete needed.
Concrete Calculator Example
Suppose you are pouring a slab that is 20 feet long, 10 feet wide, and 4 inches deep.
The base volume is approximately 66.67 cubic feet, or 2.47 cubic yards.
With a 10% waste allowance, the estimated amount increases to approximately 2.72 cubic yards.
Cubic Feet vs. Cubic Yards
Concrete is commonly ordered and sold by the cubic yard in the United States. One cubic yard is equal to 27 cubic feet.
For larger concrete projects, calculating the volume in cubic yards can make it easier to estimate the amount of concrete to order.
Frequently Asked Questions
How do I calculate how much concrete I need?
Multiply the length, width, and depth of the area to calculate the volume. The Concrete Calculator converts the result into cubic feet and cubic yards and can add a waste allowance.
How many cubic feet are in a cubic yard?
One cubic yard contains 27 cubic feet. Divide a cubic-foot measurement by 27 to convert it to cubic yards.
How much extra concrete should I order?
The appropriate waste allowance depends on the project and site conditions. The calculator lets you enter your own percentage so you can adjust the estimate for your situation.
Can I use different units for my measurements?
Yes. You can select feet, inches, yards, meters, or centimeters independently for length, width, and depth.
Does this calculator work for rectangular slabs?
Yes. This calculator is designed for rectangular areas where the length, width, and depth are known.