Concrete Calculator
Estimate concrete volume, weight, bag count, and cost for slabs, footings, and walls in seconds.
What Is a Concrete Calculator?
A concrete calculator estimates the volume, weight, bag count, and cost of concrete needed for a project, based on the dimensions you enter. Concrete itself is a mix of cement, sand, aggregate, and water, and is most commonly measured by the cubic yard (or cubic meter outside the US) once poured.
Instead of manually working out volume formulas for slabs, footings, walls, or columns, this calculator handles the math for you. It converts your project’s length, width, and depth into the exact quantity of ready-mix or bagged concrete you’ll need to order, plus an estimated cost based on regional pricing.
How to Use This Calculator
- Select your project type. Choose from slab, footing, wall, or column, depending on what you’re pouring.
- Enter your dimensions. Input the length, width, and depth (or thickness) in feet, inches, or metric units.
- Choose your concrete source. Select ready-mix or bagged concrete, depending on how you plan to order.
- Review your results. The calculator instantly shows your volume in cubic yards, cubic feet, or cubic meters, along with the estimated bag count and cost.
If you’re unsure how many cubic yards your project needs, this calculator handles that conversion automatically once you enter your measurements.
Concrete Volume Formula and Worked Example
Concrete volume is calculated using a standard geometric formula, consistent with guidelines referenced in ACI 318, the American Concrete Institute’s Building Code Requirements for Structural Concrete.
Volume (ft³) = Length (ft) × Width (ft) × Depth (ft)
To convert cubic feet to cubic yards, divide by 27, since one cubic yard equals 27 cubic feet.
Worked Example
Suppose you’re pouring a concrete slab that measures 10 feet long, 10 feet wide, and 4 inches (0.33 feet) thick.
Volume = 10 × 10 × 0.33 = 33 cubic feet
Converting to cubic yards: 33 ÷ 27 = 1.22 cubic yards
Most contractors add a waste allowance of 5 to 10 percent to account for spillage and uneven subgrade, bringing the practical order quantity to approximately 1.28 to 1.34 cubic yards.
Frequently Asked Questions
The amount of concrete you need depends on the volume of your project, calculated as length times width times depth. Enter your project dimensions into the calculator above to get an instant volume in cubic yards, cubic feet, or cubic meters, along with the estimated bag count if you plan to use bagged concrete instead of ready mix.
Multiply the length, width, and depth of your project in feet to get cubic feet, then divide by 27 to convert to cubic yards, since one cubic yard equals 27 cubic feet. For irregular shapes like stairs or columns, break the project into smaller sections and calculate each one separately before adding the totals together.
A cubic yard of standard concrete weighs approximately 4,000 pounds, or about 2 tons. This can vary slightly depending on the mix design, aggregate type, and moisture content, so always confirm the exact weight with your supplier if you need precise figures for transport or structural planning.
One cubic yard of concrete requires approximately 45 bags of 60-pound premixed concrete, or 60 bags of the 80-pound size. Bagged concrete is generally more practical for smaller projects under one cubic yard, while ready mix delivery is more cost-effective for larger pours.
Ready mix concrete is delivered by truck and is more economical for larger projects, typically anything over one cubic yard. Bagged concrete is easier to transport and mix in small batches, making it a better fit for small jobs like fence post footings or minor repairs where ordering a full truckload would not be practical.