Concrete Calculator
Work out the volume of concrete for a slab or base and how many 25kg bags of ready-mix you need.
Your result
Updates as you type. Based on 2025/26 UK figures where relevant.
How this is worked out
Length × width × depth gives cubic metres. Concrete weighs about 2.4 tonnes per m³, and a 25kg bag of ready-mix makes about 0.0115 m³.
Tips
- Find your unit rates and standing charges on your latest bill or in your supplier's app.
- Standing charges are paid every day regardless of usage.
- Always buy materials from the same batch and add a waste allowance for cuts.
Guides for this calculator
- How to Calculate Concrete Volume in the UK: Step-by-Step Guide
- Concrete Volume: Common Mistakes, Tips and FAQs
More home and energy calculators
Frequently asked questions
How does the concrete Calculator work?
Length × width × depth gives cubic metres. Concrete weighs about 2.4 tonnes per m³, and a 25kg bag of ready-mix makes about 0.0115 m³.
Where do the default energy prices come from?
They are typical UK price-cap level figures used as a starting point. Replace them with the rates on your own bill for an accurate result.
Do the DIY calculators include waste?
Most include an adjustable waste allowance. 10% is typical; complex layouts may need 15%.
Are the results exact?
They are estimates. Real usage, weather and installation details will change actual costs.
This calculator gives an estimate for general information. It isn't financial, tax, legal or medical advice. Check official figures on GOV.UK or NHS.uk, or speak to a qualified adviser.