Concrete Calculator
Estimate concrete volume for a rectangular slab, footing/block or cylindrical column, with separate dimension units and an optional extra allowance.
Calculator arithmetic runs locally in your browser and does not require an API.
The interactive calculator loads here when JavaScript is enabled.
How to use Concrete Calculator
Enter positive dimensions and the unit for each measurement. Column input is radius, not diameter. Switching units changes the meaning of the entered number; re-enter dimensions in the desired units.
Formula and method
Rectangular volume = length × width × depth. Cylinder volume = π × radius² × height. Dimensions are converted to meters first. Volume with extra = geometric volume × (1 + extra percentage/100).
Understanding the results
Cubic feet, yards and meters express the same adjusted volume. Geometric volume and the extra portion are shown separately. Actual ordering quantities depend on site conditions, supplier rules and mix yield; no bag count or engineering requirement is inferred.
Worked example
A slab 12 ft long, 10 ft wide and 4 in deep has geometric volume 40 ft³. With 10% extra it becomes 44 ft³, or about 1.62963 yd³ and 1.245941 m³.
Geometric estimates do not replace supplier specifications, site measurement or engineering requirements.
Frequently asked questions
Is depth entered in the same unit as length?
It can use a separate unit, such as feet for length and inches for depth.
Does the result tell me how many bags to buy?
No. Bag yields vary; this tool provides volume without assuming a supplier-specific yield.
Should a column use diameter or radius?
Use radius, which is half the diameter. The formula squares that radius.