Concrete Mixing Calculator For concrete and ballast volume quantity mixing calculations. To make it easier for you to calculate the volume of concrete or ballast you will need to mix we have created this easy to use concrete mixing calculator. Step 1. Enter your dimensions into the "width" and "length" fields in meters to calculate the volume of concrete required eg. 500mm = 0.50 meters.  Step 2. Click the "Volume" button to get cubic meters of concrete needed for your area.  Step 3. Then click on "Quantities" to get the breakdown of the amount of cement sand and aggregate needed. Step 4. Then to order your materials click here > Please remember that water volumes are approximate and care should be taken when adding this. Also please remember that cement can damage your skin, so wear the appropriate safety equipment using it.