Concrete Volume by Shape Calculator
Estimate concrete for rectangular, triangular, circular or irregular prisms by applying an editable shape factor to a bounding box.
Default project preview
1.28 yd³
Concrete bags
58
Bounding-box volume
1.48 yd³
Shaped volume
1.16 yd³
Volume reduction
21.5%
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Bounding length
Enter this project assumption in ft. The current imperial default is 12 ft.
Bounding width
Enter this project assumption in ft. The current imperial default is 10 ft.
Concrete depth
Enter this project assumption in in. The current imperial default is 4 in.
Shape factor
Enter this project assumption in 0–1. The current imperial default is 0.785 0–1. Minimum: 0.01. Maximum: 1.
Identical shapes
Enter this project assumption in a unitless value. The current imperial default is 1. Minimum: 1.
Extra allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Concrete yield per bag
Enter this project assumption in ft³. The current imperial default is 0.6 ft³.
Ready-mix price
Enter this project assumption in per yd³. The current imperial default is 165 per yd³. Minimum: 0.
Price per bag
Enter this project assumption in a unitless value. The current imperial default is 7. Minimum: 0.
How to read the outputs
Concrete bags
rounded full bags. Default preview: 58.
Bounding-box volume
before shape factor. Default preview: 1.48 yd³.
Shaped volume
before allowance. Default preview: 1.16 yd³.
Volume reduction
outside the shape. Default preview: 21.5%.
Placed weight
planning density. Default preview: 5,175 lb.
Cost comparison
ready-mix / bags. Default preview: $211.08 / $406.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Concrete volume = bounding length × bounding width × depth × shape factor × quantity. The allowance is applied before converting volume and rounding bags.
FAQ
Concrete Volume by Shape Calculator questions
What shape factor should a rectangle use?+
Use 1.0 because the shape fills the entire bounding rectangle.
What factor represents a circle?+
A circle whose diameter equals the bounding-box width and length uses π ÷ 4, approximately 0.785.
How should a very irregular shape be measured?+
Divide it into simpler rectangles, triangles or circles and calculate each portion separately for better accuracy.