Calculate the amount of concrete from length, width and thickness
Find the volume for a rectangular concrete slab with your own measurements. You can enter an allowance in percent and get the result in cubic meters and liters.
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Worked example
- Length: 12 ft
- Width: 10 ft
- Thickness: 4 in
- Allowance: 0 %
Result
Volume
40 ft³
Working
- 4 in = 0.3333 ft
- V = l × b × t × (1 + allowance/100)
12 ft × 10 ft × 0.3333 ft × (1 + 0/100) = 40 ft³
Measure the volume to be filled
The concrete calculator uses length, width and thickness. It calculates a geometric volume for a rectangular slab of even thickness. Use the measurements of the part to be filled with concrete.
You can enter the measurements in mm, cm or m, or in inches, feet or yards. Pay particular attention to the unit of the thickness, as it often differs from the length and width. An allowance in percent is added on top of the calculated volume if you choose to enter one.
Example with a slab of 4 m by 3 m
The slab is 4 m long, 3 m wide and 10 cm thick. The thickness is converted to 0.1 m. The area is 4 × 3 = 12 m². The volume is 12 × 0.1 = 1.2 m³. The full working is 4 × 3 × 0.1 = 1.2 m³, which equals 1.2 × 1,000 = 1,200 liters without an allowance.
Bags of concrete require the manufacturer's data
If you use concrete from bags, you need to know the finished yield per bag. The weight of the bag alone does not tell you how large a finished volume it gives. Without the manufacturer's figure for the yield, the number of bags is unknown. The calculation also does not determine the concrete mix or the required thickness of the slab.