Concrete Calculator
Estimate concrete volume and bag count for a slab using length, width, depth and bag yield.
Set your values
Adjust the values, then calculate your result.
How to use Concrete Calculator
- Enter the measurements or amounts in the fields above.
- Check that dimensions, rates and units match the labels.
- Select “Estimate concrete” to see a clear estimate and the formula used.
How the concrete calculator works
Volume in cubic metres = length × width × depth in metres. Bag count = volume in litres ÷ stated bag yield, rounded up.
Check your measurements and assumptions
The result excludes ground preparation, reinforcement, spillage and uneven excavation. Concrete mixes have different yields; check the product bag and consult local building requirements for structural work.
Review the estimate before you act
Compare this result with an independent measurement, supplier quote or institution guidance when the decision matters. Confirm that the units and assumptions match the labels above, and update the inputs when the conditions change. Keep a note of the values used so you can reproduce the estimate later. This calculator is a planning aid and does not replace professional, product-specific or local guidance.
How many bags of concrete do I need for a slab?
Convert the slab dimensions to metres, multiply them for volume, convert cubic metres to litres and divide by the bag yield.
Is input uploaded?
Processing takes place in your browser. This tool does not send your input or selected files to a conversion API.