If you’re building a structure, the foundation footing is one of the most critical elements. It provides a stable base that spreads the load of the building evenly into the ground. An essential part of getting the footing right means ensuring you have enough concrete to fill the trenches or forms accurately – without running short or wasting materials.

And while calculating concrete for a foundation footing might seem tricky at first, it can become straightforward thats to our step-by-step guide.

Of course, if you want quick results, then why not head to our online concrete calculator, and we will do the maths for you. Simply enter the length, width and height of your footing, and our handy tool will instantly give you the volume of concrete you require.

If you are working on a DIY project, it’s always important to understand how the calculation works so you can confidently make adjustments for tricky site conditions.

Step 1: Understand the dimensions of the footing

Before any calculations, you need the exact measurements of your footing design. A typical footing is rectangular in shape and is measured in three dimensions:

Length: how long the trench or footing run is.

Width: how wide the footing is, usually wider than the wall it supports.

Height / Depth (sometimes referred to as thickness): how deep the concrete needs to be.

Always double-check these measurements on your construction drawings or plans. For example, a footing might be 20 metres long, 0.5 metres wide, and 0.25 metres deep.

Step 2: Convert dimensions to a consistent unit

Concrete volume is calculated in cubic units, most often cubic metres (m³) in the UK and many other countries. To make sure your calculations are accurate, convert all dimensions to metres before multiplying.

If length = 20 m, width = 0.5 m, and depth = 0.25 m, no conversion is needed.

If your plans are in millimetres or centimetres, divide by 1,000 or 100, respectively to get metres.

Step 3: Use the volume formula

The volume of a rectangular footing is calculated using:

Volume = length × width × height

If you have multiple footings or sections, calculate each one separately and then add them together for the total volume.

Step 4: Factor in waste and over-excavation

It’s good practice to order a little more concrete than the exact calculation. Footing trenches are rarely perfectly level or square, and some spillage or over-excavation is almost inevitable.

Some tend to order five to 10 per cent extra concrete as a buffer.

Step 5: convert cubic metres to ready-mix loads

If you’re using ready mixed concrete, suppliers will deliver by the cubic metre, so you can order directly based on your calculation.

If you’re mixing your own concrete, you will need to mix with sand, gravel and water. If this is the case, you should check the mix ratio for the recommended footings.

Order ready-mixed concrete directly to your site

At Erris Concrete, we can deliver ready-mixed concrete directly to your site – whether that’s a residential or commercial area. Better still, our volumetric mixer means we can get freshly mixed concrete to you, without the risk of unnecessary expense due to over-ordering.

Use our online concrete calculator to find out how much concrete you need to order, or get in touch with a member of our friendly team.