Concrete Volume Calculator
Cubic metres and tonnes of concrete needed for a slab, with a waste allowance.
Results
Volume
1.944
m³
Volume
1.800
m³
Mass
4.666
t
What this tool does
Give the area and the thickness and this returns the volume to order, both as the bare geometric figure and with your waste allowance added. The density default of 2400 kg/m³ is typical for normal-weight reinforced concrete.
Formula
V = c × l × e , mass = V × density
Variables
| Symbol | Meaning | Unit |
|---|---|---|
l | Length | m |
w | Width | m |
h | Thickness | cm |
d | Density | kg/m³ |
wa | Waste allowance | % |
V | Volume | m³ |
Vn | Volume | m³ |
M | Mass | t |
Worked example
- Length5 m
- Width3 m
- Thickness12 cm
- Density2400 kg/m³
- Waste allowance8 %
- Volume1.944 m³
- Volume1.800 m³
- Mass4.666 t
Limitations
- Always order a little more material than the calculated quantity. Cuts, breakage and pattern matching create waste that depends on the shape of the job.
- Density changes with temperature, moisture and composition. Use a value from the supplier's data sheet whenever precision matters.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
Frequently asked questions
How much waste should I allow?
Between 5 % and 10 % for a straightforward slab on level ground, and more if the base is uneven, the formwork is irregular or you are pouring by hand. Running out of concrete mid-pour creates a cold joint, which is far more expensive than a little extra material.