🧊 Concrete Calculator – Free Online DIY Tool
Calculate concrete volume needed for slabs, footings, and foundations. 100% free, no sign-up required.
Volume Needed: 0 m³
With Wastage: 0 m³
How to Use the Concrete Calculator
The Concrete Calculator is a simple yet essential tool designed to help you work out exactly how much concrete you need for any project. Whether you're pouring a slab for a shed, laying a foundation for an extension, or setting fence posts, this tool takes the guesswork out of your project.
Step 1: Select the shape of your project — rectangle, circle, or cylinder.
Step 2: Enter the dimensions of your project.
Step 3: Enter the depth or thickness of the concrete.
Step 4: Choose your wastage allowance.
Step 5: Click "Calculate Concrete" and the tool will tell you exactly how many cubic metres you need.
Why Use a Concrete Calculator?
Concrete is heavy and expensive. Buying too much is a waste of money and difficult to dispose of. Buying too little means delays and extra delivery charges.
This concrete calculator helps you:
- Save money – buy exactly what you need
- Reduce waste – no excess concrete to dispose of
- Plan your budget – know exactly how much your project will cost
- Avoid delays – order the right amount the first time
Whether you're a DIY enthusiast or a professional builder, this tool is essential for any concrete project.
Understanding Concrete Measurements
Concrete is measured in cubic metres (m³). One cubic metre of concrete weighs approximately 2.4 tonnes.
The formula for calculating concrete volume is simple:
- Rectangle: Length x Width x Depth
- Circle: π x (Diameter/2)² x Depth
- Cylinder: π x (Diameter/2)² x Depth
Always add a wastage allowance of at least 10% for spills, uneven ground, and over-excavation.
How Much Concrete Do I Need?
Here are some typical concrete quantities for UK projects:
- Shed base (3m x 2m x 0.1m): 0.6 m³
- Patio (4m x 4m x 0.1m): 1.6 m³
- Driveway (5m x 3m x 0.15m): 2.25 m³
- Fence post hole (0.3m x 1m): 0.07 m³ per post
- Foundation trench (10m x 0.5m x 0.5m): 2.5 m³
These are estimates – always use the concrete calculator for an accurate measurement for your specific project.
Frequently Asked Questions
1. How do I calculate concrete for a slab?
Measure the length, width, and depth of the slab in metres, then multiply them together. Our calculator does this for you automatically.
2. How many bags of concrete do I need?
For a 20kg bag of concrete, you get approximately 0.01 m³. Divide your total volume by 0.01 to get the number of bags.
3. What is the standard concrete mix ratio?
A standard mix ratio is 1 part cement : 2 parts sand : 4 parts aggregate. For ready-mix concrete, just order by cubic metres.
4. How much wastage should I allow for concrete?
10% is standard for most concrete projects. Add more for complex shapes or difficult access.
5. How deep should a concrete slab be?
For garden sheds, 75-100mm is sufficient. For driveways and garages, 150-200mm is recommended. Always check local building regulations.
6. How much does concrete cost in the UK?
Ready-mix concrete typically costs £100-£150 per cubic metre, plus delivery charges. Prices vary by region and quantity.
7. What if my area isn't a perfect rectangle?
Break your area into rectangles, calculate each separately, then add them together. Add wastage on the total.
8. Can I use this calculator for footings?
Yes, enter the length, width, and depth of your footing trench. The calculator will give you the volume needed.
Related Tools
If you found this concrete calculator useful, you might also like these related DIY tools:
- Paint Calculator – work out how much paint you need
- Tile Calculator – calculate how many tiles you need
- Flooring Calculator – work out how much flooring you need
- Decking Calculator – calculate how many decking boards you need