How the concrete calculator works
Concrete volume is calculated by multiplying the length, width, and thickness of the area you want to fill.
For metric measurements, enter the length and width in meters and the thickness in centimeters. For imperial measurements, enter the length and width in feet and the thickness in inches.
Calcrete automatically converts the result and displays the amount of concrete required in both cubic meters (m³) and cubic yards (yd³).
Why we recommend 10% extra
The exact calculated volume assumes that every measurement is perfect and that the surface beneath the concrete is completely even. Real projects rarely work that way.
Small variations in excavation depth, uneven ground, formwork, spillage, and measurement differences can all increase the amount of concrete actually required.
For that reason, Calcrete also displays a recommended order quantity that includes 10% additional concrete. This is a general allowance rather than a requirement. Large or unusual projects may require a different allowance.
Example concrete calculation
Suppose you're pouring a slab that is 5 meters long, 3 meters wide, and 10 centimeters thick.
The exact calculated volume is 1.5 cubic meters.
Adding the 10% allowance gives a recommended quantity of approximately 1.65 cubic meters.
You can enter those dimensions into the calculator above to see the equivalent volume in cubic yards automatically.
Measuring your project
Measure the inside dimensions of the area that will actually contain the concrete. Use the longest practical measurements rather than estimating from plans when the site is already prepared.
For rectangular slabs, patios, paths, pads, and similar projects, measure the length, width, and average thickness.
If the excavation has noticeably different depths, calculating several sections separately will usually give you a better estimate than treating the entire project as one uniform slab.
Cubic meters and cubic yards
Ready-mix concrete is normally ordered by volume rather than by surface area.
A cubic meter represents a volume measuring one meter long, one meter wide, and one meter high. A cubic yard represents a volume measuring one yard in each dimension.
Calcrete shows both units regardless of whether you enter your dimensions using metric or imperial measurements, making it easier to compare your calculation with the units used by your concrete supplier.
Frequently asked questions
Does the calculator include waste?
The main result shows the calculated volume from the dimensions you entered. The recommended order shown separately includes an additional 10%.
Should I always order 10% extra?
Not necessarily. The 10% figure is a practical general allowance for small variations, uneven ground, spillage, and measurement differences. Your actual requirements depend on the project and site conditions.
Can I use the calculator for a concrete slab?
Yes. Rectangular slabs, patios, shed bases, driveways, paths, and similar projects can be calculated from their length, width, and thickness.
What if my project isn't rectangular?
Divide an irregular area into simpler sections where possible, calculate each section separately, and add the volumes together.
Why is concrete measured by volume?
Concrete fills three-dimensional space, so surface area alone isn't enough to determine how much you need. Thickness has a direct effect on the total quantity required.
Before you order
Calcrete provides an estimate based entirely on the dimensions you enter. Actual concrete requirements can vary because of excavation depth, ground conditions, formwork, compaction, spillage, and other site conditions.
For large pours, structural work, or projects where running short would be particularly expensive, confirm the required quantity with your concrete supplier or contractor before ordering.