Concrete Calculator Guide
Learn which measurements matter, how concrete volume is calculated, and how to add a sensible waste allowance before ordering.
Open calculatorMeasure first. The formula does the rest.
Use consistent units for every measurement. Keep the original values precise; only round the final quantity you plan to buy.
See the calculation change
This is an interactive example, not a replacement for checking the material manufacturer's specifications.
How the calculation works
Volume = Length × Width × Depth
Measure the slab, footing or form length, width and depth.
Convert measurements to consistent units before multiplying.
Add your chosen waste allowance and round only the purchase quantity.
Before you buy
- ✓Confirm the required concrete strength and mix with your supplier.
- ✓Use the actual depth rather than an average unless the project design specifies otherwise.
- ✓Keep a small waste allowance for uneven ground, spillage and measuring variation.
Common questions
Why add waste to concrete?
Small losses can happen during mixing, pouring and site preparation. The right allowance depends on the project; the calculator lets you choose it rather than hiding an assumption.
Should I order exactly the calculated volume?
Usually not. Concrete is commonly ordered with a practical allowance, but the correct amount depends on the job and supplier minimums.
Does the calculator know my concrete mix?
No. Volume is geometric. Mix strength, density and delivery requirements should come from the concrete supplier.