Concrete Calculator
Calculate the volume of concrete and the number of cement bags.
Tip: Add 5–10% extra to the calculated volume for losses during the work.
Did this tool help?
About this digital tool
The concrete calculator helps you find how many cubic metres of concrete you need for a slab, a column or a round post, and how many bags of cement, sand and gravel that volume requires. Choose the type of structure, the mix (1:2:4, 1:1.5:3 or 1:1:2) and the dimensions, and the result appears instantly.
The calculation is based on geometric volume: length × width × thickness for the slab, length × width × height for the column and π × (diameter/2)² × height for the round shape. The tool automatically adds 10% for waste, then multiplies the volume by the amount of cement per m³ for the mix and divides by 50 kg bags. It is useful for builders, for owners making foundations, terraces or bases, and for anyone who wants to order concrete without leftover waste.
How to use
- Choose the type of structure: slab, column or round shape.
- Choose the concrete mix: 1:2:4, 1:1.5:3 or 1:1:2.
- Enter the dimensions: length, width and thickness (cm) or height (m), or the diameter for the round shape.
- Read the volume in m³, the number of cement bags and the amount of sand and gravel.
Frequently asked questions
How much cement is needed for 1 m³ of concrete?
It depends on the class. For C20/25 concrete (ordinary): ~300 kg of cement, ~700 kg of sand, ~1,200 kg of gravel and ~150 L of water per m³.
How is the volume of concrete for a slab calculated?
Multiply the length by the width and by the thickness expressed in metres. For example, a 5 × 4 m slab 15 cm thick has 5 × 4 × 0.15 = 3 m³ of concrete. The tool does this conversion itself when you enter the thickness in cm.
What does the 1:2:4 mix in concrete mean?
The numbers show the parts by volume of cement, sand and gravel. The 1:2:4 mix is the standard for ordinary work, while 1:1:2 has more cement and gives stronger but costlier concrete. Choose it according to the project's requirements.
Is waste included in the calculated amount of concrete?
Yes, the calculator adds 10% to the theoretical volume for pouring, spillage and small errors in the formwork. The waste row appears in the results, so you know how much has been added.