Practical guide
How to Calculate Concrete Volume in South Africa
Calculate concrete volume by converting every dimension to metres and multiplying length × width × depth. Keep measured volume separate from allowance and supplier rounding.
Updated 15 October 2026
Reviewed by the 99tools team. Editorial and corrections policy.
| Illustrative area | Illustrative depth | Measured volume, no allowance |
|---|---|---|
| 20 m² | 75 mm | 1.5 m³ |
| 20 m² | 100 mm | 2 m³ |
| 20 m² | 150 mm | 3 m³ |
| 35 m² | 120 mm | 4.2 m³ |
Quick answer: the concrete calculator formula
For a rectangular section, m³ = length in metres × width in metres × depth in metres. A 5 m × 4 m area at 100 mm depth contains 2 m³. The same formula is area in m² multiplied by depth in metres. A depth is always needed to convert square metres into cubic metres.
Convert the units before multiplying
Divide millimetres by 1,000 or centimetres by 100 to obtain metres. Keep a record of the entered unit for each field. A 100 mm thickness is 0.1 m; entering 100 in a metre field would multiply the depth by 1,000. Check dimensions before considering an allowance.
Add different shapes carefully
Split an irregular project into measured non-overlapping sections. Add the volumes. A repeated count is suitable only for identical sections. Cylindrical volume is pi × diameter² ÷ 4 × depth, with dimensions in metres. Subtract a known displaced volume once when it should not contain concrete.
Measured volume and ordered volume
An agreed percentage can cover the measured project’s expected variation or losses. In the example, 2 m³ plus 5% gives 2.1 m³. If a supplier requires an increment, round the allowed quantity upward to that increment. Do not round each measured section early or apply the percentage twice.
Litres and yards are different displays of volume
Multiply m³ by 1,000 for litres. Divide m³ by 0.764554857984 for cubic yards. The main calculator displays all three. A cubic yard describes volume, whereas a square yard is area and still needs a depth.
Volume does not choose a concrete specification
The thicknesses in examples demonstrate multiplication only. Concrete strength, reinforcement, foundation design, site preparation and curing must come from the actual specification. A calculator cannot turn an unspecified area into a safe structural design.
Use the related calculators
Apply the explanation above with your own figures. Open a calculator below, check every input and review the result assumptions before making a decision.
Frequently asked questions
What is the concrete volume formula?
Length × width × depth in metres, or area in m² × depth in metres.
How do I convert m² to m³ of concrete?
Multiply the area by the concrete depth in metres. Area alone is not enough.
Do I need to order exactly the measured volume?
Agree any allowance and order increment with the supplier and responsible contractor. Keep them separate from the measured quantity.