Concrete Block Calculator
Calculate how many concrete blocks you need for a wall, based on the wall's dimensions and block size.
How to use the calculator
- Measure the length and height of the wall to be built.
- A standard concrete/cinder block is often 39 × 19 cm — adjust if you're using a different size.
- The calculator works out the wall area and number of blocks, with 5% extra for waste and cutting.
How is it calculated?
The calculation doesn't account for openings like doors and windows — subtract the area of such openings from the wall area before using the calculator for a more accurate figure.
Frequently asked questions
Why is 5% extra added?
To cover cuts at corners and edges, as well as any breakage or miscuts during construction — a common, conservative allowance in the building industry.
How do I subtract doors and windows?
Calculate the area of each opening (width × height) and subtract the total from the wall area manually, or reduce the wall length/height accordingly before using the calculator.
Is this enough to order materials?
It gives a good estimate for simple projects, but for larger or load-bearing walls, always check with your supplier or a professional for exact order quantities and any mortar/reinforcement needed.