Concrete Block Wall Calculator
For foundations, garden walls and partitions in standard concrete block. Enter the wall size and get course counts, blocks to buy and mortar.
Your results
Worked example
A 6 m long, 2.4 m high wall in standard block
Standard block lays on a 400 x 200 mm module with joints: ceil(6 ÷ 0.4) = 15 blocks per course and ceil(2.4 ÷ 0.2) = 12 courses, so 15 × 12 = 180 blocks. With 5 percent waste: 189 to buy. Mortar at 15 blocks per bag: 180 ÷ 15 = 12 bags. The same wall in imperial (20 ft by 8 ft, 16 x 8 in modules) gives the identical 180 blocks.
How this calculator works
Block walls are counted on the module, not the block: a standard 390 x 190 mm block plus a 10 mm joint occupies 400 x 200 mm of wall. blocks per course = ceil(wall length ÷ 0.4); courses = ceil(wall height ÷ course module). Epsilon-safe ceiling keeps a wall that lands exactly on the module from gaining a phantom course. Openings are not subtracted automatically; for a door or window, subtract its area in blocks (opening width ÷ 0.4, rounded up, times opening height in courses) or shorten the wall length for full-height openings.
The 6-inch block option (390 x 140 mm face) lays on a 400 x 150 mm module: the same 6 x 2.4 m wall needs 16 courses and 240 blocks.
Common questions
How many blocks are in a square metre of wall?
At the standard 400 x 200 mm module, exactly 12.5 blocks per square metre (about 1.16 per square foot). Multiply your wall area by 12.5 for a quick check against this calculator's course-by-course count.
Does this include blocks for corners and lintels?
The count is for the plain wall field. Corners reuse the same blocks in standard running bond, but lintel (bond beam) blocks over openings, pilasters and half blocks for closures are extras; the waste allowance covers small numbers, and larger features should be counted separately.
What about retaining walls?
Retaining walls use interlocking segmental blocks, not CMU and mortar; the retaining wall block calculator on this site handles those. This page is for mortared concrete block.
Estimates only, for quantity planning. Structural walls, foundations and reinforcement follow your drawings, engineer and local building code.