Construction materials
Mortar and concrete calculator
Calculate your project volume and, if you know the manufacturer yield, the approximate number of bags.
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Before placing an order
The yield of each mortar or concrete product depends on its formulation and application. Always confirm it with the manufacturer technical sheet.
Calculation guide
How to calculate mortar and concrete for slabs and fills
Convert site measurements into cubic metres and use the manufacturer yield to estimate bags.
Enter length, width and thickness. The calculator converts thickness from millimetres to metres and returns cubic metres; a 5 m by 4 m slab at 100 mm needs 2 m³ before allowance. Split the project into areas when levels, slopes or thicknesses differ.
The allowance covers uneven ground, mixing losses and level adjustments. Five percent may suit a regular base, while 10% or 15% can be safer for fills or irregular excavations. Even a small change in thickness makes a substantial difference across a large area.
To estimate bags, enter the stated m³ yield for the exact product. Mortars and concretes do not share the same yield, and it changes with formulation, mixing water and application. Reinforcement, additives, curing and structural design are outside this estimate and should be checked before ordering.
Methodology and contents updated on 14 July 2026.
Frequently asked questions
Quick answers before buying
How is concrete volume calculated?
Multiply length by width by thickness in metres. Divide millimetres by 1,000 first.
How much allowance should I add?
Use 5% to 15%, depending on the base regularity and the work complexity.
How do I calculate mortar bags?
Enter the manufacturer yield in m³ per bag and the calculator rounds bags up.
Can I use this for structural elements?
It estimates quantity only; a structural mix and system must be technically specified.
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