Building and decorating
Concrete Volume Calculator
Estimate the volume for a slab, footing or solid round column, then turn it into an order allowance or bag count.
Find another tool
This tool needs JavaScript. If the controls don’t appear, check your connection, enable JavaScript and reload this page.
How to use this tool
1. Enter your own figures below, or choose Load example to try the worked example. Check the units beside each field.
2. Select Calculate to see the result and its breakdown. If you change an input, calculate again before copying or printing.
3. Use Copy summary or Print / save PDF to keep your assumptions and results together. Reset clears the form.
How the calculation works
Rectangular volume = length × width × depth. Cylinder volume = π × (diameter ÷ 2)² × height. Depth or height is converted from millimetres to metres. Multiply by the number of identical shapes and then by (1 + allowance percentage). A cubic metre is 1,000 litres. Bag count divides the unrounded allowance volume by the entered bag yield and rounds up.
Worked example
A 5 m × 4 m slab at 100 mm depth has a measured volume of 2 m³. Adding 10% gives 2.2 m³, or 2,200 litres. At an entered yield of 10 litres per bag, that is 220 bags.
Questions and assumptions
What this estimate includes
The cylinder is solid: posts, pipes and other voids are not subtracted. Run separate calculations for different shapes and dimensions. Site tolerances, uneven ground, pump loss, supplier minimums, reinforcement and structural strength are not modelled. The allowance is your chosen assumption, not a specified industry requirement.
Can I save or share my result?
Copy summary includes the current inputs and results. Print / save PDF creates a local report with the calculation scope and source links. Your figures are not added to the page URL or stored by this tool. Refreshing clears the form.
Sources and further reading
Built and maintained by Custom Logic. Page updated .