Block Wall Calculator — Blocks, Mortar & Reinforcement
Blocks, mortar or thin-bed adhesive, bed reinforcement, vertical bars, grout and lintels for a wall in concrete or lightweight blocks. The block size is an input rather than an assumption, so the wall is counted in the unit actually sold where you are.
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Plan the whole job — not just this calculation
Save results to a project: budget and shopping list build themselves, and the whole plan exports as a PDF. Draw your floor plan and room sizes pre-fill the calculators.
Free covers one project, three saved calculations and a two-room plan. What a Project Pass adds →
How the block wall calculator works
- 1Net area = length × height, less any openings
- 2Blocks per unit area come from the laid size — the block plus one joint each way. A 390 × 190 mm block at a 10 mm joint covers 0.08 m², so 12.5 blocks per m²; a 16 × 8 in block at a ⅜ in joint gives about 1.16 per sq ft
- 3Blocks = net area × that figure, plus breakage
- 4Courses = height ÷ (block height + joint), rounded up
- 5Mortar is derived from the joints themselves rather than a published rate: bed length × bedding depth × joint thickness, plus a perpend between each pair of blocks
- 6Thin bed instead: adhesive by weight per unit area, as printed on the bag
- 7Bed reinforcement every n courses; vertical bars at their spacing, priced by weight, with grout for each filled cell
Worked example
18 m × 2.4 m wall (59 × 8 ft) in 390 × 190 × 190 mm blocks — 16 × 8 × 8 in — with 10 mm (⅜ in) joints, fully bedded.
43.2 m², or 465 sq ft: 567 blocks in 12 courses, and 601 litres of mortar — 21 cu ft, which is 41 bags of 15 litres (4 gal). Per unit area that is 13.9 litres per m², or 0.05 cu ft per sq ft.
Frequently asked questions
How many blocks are there in a square metre?
One divided by the laid size: block length plus a joint, times block height plus a joint. A 390 × 190 mm block at a 10 mm joint gives 12.5 per m²; a 16 × 8 in block at a ⅜ in joint gives about 1.16 per sq ft. Type the size you can buy and the figure follows it.
Full bedding or face-shell bedding?
The form opens on full bedding, where mortar covers the whole block width — correct for solid units, and the safe direction to be wrong in. Hollow blocks are normally bedded on the shells only, which is nearer a third of the mortar. Set the bedding depth to the shell width, around 30 mm or 1¼ in, and the mortar figure follows.
Does it handle thin-bed adhesive?
Yes. Switch the joint to thin bed and mortar is replaced by adhesive at the rate per unit area from the bag, with the joint down to the 2–3 mm (⅛ in) a glued course takes. Blocks, courses and reinforcement are unchanged.
Plan the whole job
One calculation is one line of a job. With the floor planner you draw the room once and every calculator on the site fills itself from those measurements, with the openings taken off. The project manager then holds every room and trade against one budget, and tracks what things actually cost as the invoices arrive.