Concrete Calculator
Estimate concrete volume for rectangular slabs or round columns, with optional waste allowance.
Runs in this browser. No upload by this tool. Copy/download/export locally.
Dimensions
Concrete volume
Choose a shape and units, then enter the finished dimensions.
This estimates geometric volume only. Job-site conditions, excavation, overbreak, spillage, reinforcement, mix design, and supplier minimums are outside the calculation.
Result
Result
—Export result
Copy a readable summary or download the current result as a local file.
Create a valid result to enable local exports.
How Concrete Calculator works
Use the calculator first. The sections below explain the inputs, worked examples, method, outputs, and limits.
How to use
- Choose slab/rectangle or round column.
- Choose US or metric units.
- Enter the dimensions shown for that shape.
- Optionally enter a waste allowance percentage.
- Review cubic yards, cubic feet, and cubic meters, then export locally.
Worked examples
Slab example
A 20 ft × 12 ft slab at 4 in thick has a base volume of about 2.96 yd³.
Waste example
Adding 10% to that 2.96 yd³ geometric volume produces about 3.26 yd³.
Metric slab
A 6 m × 4 m slab at 10 cm thick has a base volume of 2.4 m³.
Round column
A 12 in diameter column 8 ft high uses the cylinder formula and is much smaller in volume than an equivalently tall rectangular prism.
Result reference
Cubic yards
US suppliers often quote ready-mix concrete by cubic yard. 1 cubic yard = 27 cubic feet.
Cubic meters
Metric volume is reported in cubic meters after dimension conversion.
Waste allowance
Order volume = base geometric volume × (1 + waste percentage ÷ 100).
Round columns
Cylinder volume uses π × radius² × height.
FAQ
What does the concrete calculator estimate?
It estimates geometric concrete volume for either a rectangular prism or a round cylinder, then optionally adds a waste percentage.
What units are supported?
US mode accepts feet for slab length/width and column height, inches for thickness/diameter, and reports cubic yards prominently. Metric mode uses meters and centimeters and reports cubic meters prominently.
How is slab volume calculated?
Length × width × thickness after converting all dimensions to compatible units.
How is round-column volume calculated?
π × radius² × height after converting the dimensions to compatible units.
What is the waste allowance?
It increases the base geometric volume by the percentage you enter. It is not a recommendation for a specific project.
Why does the result also show other volume units?
Equivalent cubic feet, cubic yards, and cubic meters help with plans, supplier orders, and cross-checking.
Does this calculate concrete bags?
No. Bag yields vary by product, mix, and package size, so this version does not guess a bag count.
Does this account for rebar or forms?
No. Those affect project planning but are not subtracted from the geometric concrete volume here.
Is this a final material order?
No. Verify dimensions, job-site conditions, and supplier requirements before ordering.
Are project dimensions saved?
No. This tool does not persist dimensions after the page is closed or cleared.
Method & limitations
Rectangle
Volume = length × width × thickness after unit conversion.
Round column
Volume = π × (diameter ÷ 2)² × height.
Conversions
1 yd³ = 27 ft³; 1 ft³ = 0.028316846592 m³.
Scope
Geometric volume is an estimate, not a supplier quantity recommendation.
Verify dimensions and local supplier/job-site requirements before ordering concrete. This tool does not account for field conditions or construction tolerances.