Concrete Calculator
Estimate the volume of a rectangular concrete slab.
Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations retain full precision.
Example Calculation
- Length: 5 m
- Width: 4 m
- Thickness: 10 cm
- Extra allowance: 5 %
A 5 × 4 m slab, 10 cm thick, needs 2 m³ before allowance.
Frequently asked questions
How do I use this calculator?
Enter length, width, thickness, extra allowance. The result updates automatically. Use Reset to restore the example values.
What method does it use?
Volume = length × width × thickness. Follow the units and definitions shown with the inputs to apply this relationship consistently.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.