To calculate concrete for footings, columns or beams, find the volume of each member and add the results together. For rectangular sections, the basic calculation is length x width x depth or height. The final quantity can then be converted into cubic metres, cubic feet or another unit used for ordering.
For structural work, the dimensions and reinforcement should come from the building drawings or instructions from the responsible engineer or building professional. The calculations below show how to determine the concrete quantity once those dimensions are known.
Table of Contents
- The basic concrete volume formula
- How to calculate concrete for footings
- How to calculate strip footing concrete
- How to calculate concrete for columns
- How to calculate concrete for circular columns
- How to calculate concrete for beams
- How to calculate the total concrete quantity
- How much extra concrete should I allow?
- Does reinforcement change the concrete volume?
- Common concrete quantity mistakes
- Use a concrete calculator
- Frequently asked questions
The Basic Concrete Volume Formula
The starting point is simple: calculate the volume of the concrete shape. For a rectangular member, multiply its length by its width and its depth or height.
Keep all measurements in the same unit before calculating. If the result needs to be in cubic metres, convert the dimensions to metres first.
For example, a beam that is 6 metres long, 0.25 metres wide and 0.40 metres deep requires:
For a more general calculation involving different shapes and units, use the Concrete Volume Calculator.
How to Calculate Concrete for Footings
A rectangular isolated footing can be calculated in the same way as any rectangular block. You need the footing length, width and thickness.
Example: One Rectangular Footing
Suppose a footing measures:
- Length = 2.0 m
- Width = 2.0 m
- Thickness = 0.30 m
The volume is:
So one footing has a calculated concrete volume of 1.20 m³.
If there are eight identical footings:
How to Calculate Strip Footing Concrete
Strip footings are usually long, continuous foundations beneath walls. Their volume can be calculated by multiplying the total footing length by the footing width and thickness.
Example: Strip Footing
Assume a strip footing is 24 metres long, 0.60 metres wide and 0.25 metres thick.
If the foundation changes size along its length, divide it into sections. Calculate each section separately and add the volumes.
How to Calculate Concrete for Columns
A rectangular or square column is calculated from its cross-sectional dimensions and height.
Example: Square Concrete Columns
Suppose one column is:
- Width = 0.30 m
- Depth = 0.30 m
- Height = 3.0 m
Its concrete volume is:
For ten identical columns:
When calculating several columns, check whether all of them have the same cross-section and height. If their dimensions differ, calculate each group separately.
How to Calculate Concrete for Circular Columns
Circular columns require a different formula because their cross-section is a circle.
If the column diameter is known, divide the diameter by two to find the radius.
Example: Circular Column
Consider a circular column with a diameter of 0.40 m and a height of 3.0 m.
First calculate the radius:
Then calculate the volume:
Rounded to two decimal places, the column requires approximately 0.38 m³ of concrete.
How to Calculate Concrete for Beams
For a rectangular beam, multiply the beam length by its width and depth.
Example: Concrete Beam
Suppose a beam is 8 metres long, 0.25 metres wide and 0.45 metres deep.
If there are four beams with these same dimensions:
So the calculated volume for the four beams is 3.60 m³.
How to Calculate the Total Concrete Quantity
For a project containing footings, columns and beams, calculate each structural element separately and then add the volumes.
For example, imagine a small structure has:
| Element | Quantity | Volume Each | Total Volume |
|---|---|---|---|
| Footings | 8 | 1.20 m³ | 9.60 m³ |
| Columns | 10 | 0.27 m³ | 2.70 m³ |
| Beams | 4 | 0.90 m³ | 3.60 m³ |
Add the three totals:
This gives the theoretical volume based on the dimensions used in the calculation. The quantity ordered or mixed may need an additional allowance depending on the project and supply method.
How Much Extra Concrete Should I Allow?
The calculated volume and the amount delivered or mixed are not always identical. Small losses can occur through spillage, uneven excavation, formwork variations, ground conditions and other site factors.
A percentage allowance can therefore be considered after calculating the theoretical quantity. For example, a 5% allowance on 15.90 m³ would be:
Adding that allowance gives:
That is approximately 16.70 m³.
Does Reinforcement Change the Concrete Volume?
Reinforcing bars occupy some physical space inside concrete, but concrete quantity calculations for ordinary estimating are commonly based on the designed concrete dimensions rather than subtracting the volume of every reinforcement bar.
The more important point is to keep the concrete and reinforcement calculations separate:
- Concrete quantity is calculated from the designed concrete dimensions.
- Rebar quantity is calculated from bar diameter, spacing, lengths, bends, laps and the structural drawings.
- Formwork measurements are a separate quantity calculation.
For reinforcement quantities, use the Rebar Calculator and the supporting article How to Calculate Rebar Quantity for Concrete.
Footings, Columns and Beams: Quick Formula Reference
| Structural element | Basic calculation |
|---|---|
| Rectangular footing | Length x Width x Thickness |
| Strip footing | Total Length x Width x Thickness |
| Square column | Width x Depth x Height |
| Rectangular column | Width x Depth x Height |
| Circular column | 3.14159 x Radius x Radius x Height |
| Rectangular beam | Length x Width x Depth |
| Multiple identical members | Volume of one member x Number of members |
| Combined concrete quantity | Add the volumes of all members |
Common Concrete Quantity Mistakes
Mixing measurement units
Using metres for one dimension and centimetres or millimetres for another can produce a major error. Convert all dimensions to the same unit before multiplying.
Using the wrong footing dimensions
Foundation drawings may contain different widths, thicknesses or stepped sections. Do not assume every footing has the same size.
Forgetting the number of members
Calculating one column correctly does not give the total quantity when the project has several columns. Multiply the volume of one identical member by the number required.
Ignoring changes in section size
Some beams, columns and foundations have different dimensions in different locations. Group identical members and calculate different sizes separately.
Confusing concrete volume with material quantities
A result such as 5 m³ describes the volume of concrete. It does not directly tell you how many bags of cement, how much sand or how much aggregate are required. Those quantities depend on the specified mix and material properties.
For cement calculations, see How Much Cement Do I Need for Concrete?. You can also use the Cement Calculator.
Use a Concrete Calculator
Once you know the dimensions of your footing, column or beam, the Concrete Volume Calculator can help calculate the required volume.
For slabs and other flat areas, use the Concrete Slab Calculator.
If your project contains several types of materials and quantities, the Construction Material Estimator can be useful for broader project estimates.
Frequently Asked Questions
How do I calculate concrete for a footing?
Multiply the footing length by its width and thickness. For multiple identical footings, multiply the volume of one footing by the number of footings.
How do I calculate concrete for a column?
For a rectangular column, multiply width by depth by height. For a circular column, use the circle volume formula: 3.14159 x radius x radius x height.
How do I calculate concrete for a beam?
For a rectangular beam, multiply the beam length by its width and depth. If several beams have the same dimensions, multiply the volume of one beam by the number of beams.
Should I add extra concrete to my calculated quantity?
A project may require an allowance for losses or measurement variations, but there is no single percentage that applies to every project. Consider the site conditions, measurement accuracy and supplier requirements before ordering.
Does rebar need to be deducted from concrete volume?
For ordinary quantity estimating, concrete is generally calculated from the designed concrete dimensions. Reinforcement is normally estimated separately from the structural drawings.
Can I use this method for foundations and structural concrete?
The volume formulas can calculate the quantity from known dimensions. However, the dimensions themselves should come from the structural design or other appropriate project documentation.
What is the difference between concrete volume and cement quantity?
Concrete volume is the amount of finished concrete, usually expressed in cubic metres or cubic feet. Cement is one component of the concrete mix, so cement quantity must be calculated separately using the specified mix or cement content.