How to use the Concrete Calculator
The concrete calculator estimates the volume of concrete and the number of bags for a slab.
Open the Concrete Calculator →
What you need to enter
- Length (ft)
- Width (ft)
- Thickness (in)
- Extra for waste (%)
The formula
Volume = length × width × thickness, plus extra for waste. 1 cubic yard = 27 cubic feet. An 80 lb bag yields about 0.6 cubic feet.
Worked example
Using the default values in the calculator:
- Length (ft): 10
- Width (ft): 10
- Thickness (in): 4
- Extra for waste (%): 10
| Cubic yards | 1.36 |
| Cubic metres | 1.04 |
| 80 lb bags | 62 |
| 60 lb bags | 82 |
Tips for better results
- Order about 10% extra.
- Check thickness requirements for your project.
Common mistakes to avoid
- Mixing inches and feet.
- Forgetting waste.
Please note: Results are estimates for general use. For safety-critical work such as electrical or building projects, check with a qualified professional and local codes. See our Disclaimer.