The Block CalculatorHow does this block calculator for wall work?
Measure each wall on its own and run the calculator once per wall. For an L-shaped or rectangular building, measure the outside of one wall and the inside of the next so the corners are not counted twice. Add the results, then add your waste allowance.
Step-by-step wall takeoff
- 1. List every wall with its length and height.
- 2. Subtract openings: doors and windows (width × height) are removed from each wall’s area.
- 3. Calculate blocks for each wall with this tool.
- 4. Add 5–10% for waste, cuts and breakage.
Formula used
Total Blocks = (Wall Length × Wall Height) ÷ (Block Length × Block Height)The result is always rounded up to the next whole block, because you can’t buy part of one. Wall thickness is shown in the diagram but does not change the count for a single-wythe wall.
Example
Scenario: A wall 10 m long and 2 m high, built with blocks measuring 40 cm × 20 cm (0.4 m × 0.2 m).
Wall area: 10 m × 2 m = 20 m²
Block face area: 0.4 m × 0.2 m = 0.08 m²
Final result: 20 ÷ 0.08 = 250 blocks. Add 5–10% for cuts and breakage when you order.
Frequently asked questions
How do I handle corners?
Measure one wall on its outside face and the joining wall between the corners, so the corner block is counted only once.
How do I subtract a window?
Multiply the opening width by its height and subtract that from the wall area before dividing by the block area.
Last updated: . Results are estimates — see our disclaimer.