Home Improvement
Block Calculator
Enter wall size and block face size to see how many blocks to order.
How many blocks for a wall?
Concrete block counts start from wall area divided by the face size of one block as laid (length × height), then add waste for cuts and breakage. Enter wall length and height plus the block face dimensions from the product sheet — common metric faces are around 440 × 215 mm. Mortar joints slightly shrink the effective face; for a tighter take-off, reduce block length and height by the joint thickness before calculating. Openings for doors and windows should be subtracted from the wall area first. This is a quantity estimate, not a structural design. Brickwork uses the same idea in the brick calculator.
Worked example
A 6 × 2.1 m wall is 12.6 m². A 440 × 215 mm face is 0.0946 m² → about 133 blocks before waste. With 5% waste, round up to 140 blocks; at £1.80 each ≈ £252.
Limits and assumptions
Not a structural, lintel or wind-load design. Bond patterns at corners and piers can change real counts versus a flat-area model.
Frequently asked questions
How do I treat doors and windows?
Subtract each opening’s width × height from the wall area before running the calculator.
Hollow versus solid blocks?
Face size drives the count. Weight, thermal performance and price differ — check the product you are ordering.
Why might corners need extra blocks?
Returns and bonded corners use blocks in two planes; a single-face area model can under-count slightly.
Is mortar included?
No. Ask your merchant for mortar estimates or calculate joints separately.