Block Wall Calculator — m to blocks, mortar, cost
How to use this calculator
Enter wall length and height, then choose the unit (m, cm, or mm) from the dropdown next to each input. Select a block size, set mortar joint thickness and waste allowance. Results update instantly with block count, mortar bags, wall area, and weight.
Openings — subtract doors and windows by entering count and average size.
Grout — choose fill pattern: every course, every other, or bond beam only.
Vertical rebar — set bar diameter and cell spacing.
Horizontal rebar — bond beam blocks at course spacing intervals.
Cost — per block, per mortar bag, per rebar bar. Select your currency.
Labor — rate per m2, per block, or flat price.
Saved Calculations
| Time | Size | Blocks | Mortar | Area m2 | Material | Labor | Total |
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How to Calculate CMU Blocks for a Wall (Metric)
This block wall calculator estimates the number of concrete masonry units (CMUs), mortar bags, grout volume, and rebar for walls of any size. Enter wall length and height, and choose the unit (m, cm, or mm) from the dropdown next to each input. Choose from four standard metric block sizes: 390x190x190 mm (most common), 390x190x90 mm half, 390x190x290 mm for wider walls, and 390x190x140 mm for partitions. Subtract door and window openings, and set waste allowance from 5% to 25%.
Formulas Used
Wall area (m2) = length x height - openings. Blocks per m2 = 12.5 for 390x190 nominal (actual 390x190 with 10 mm joint = 400x200 module). Mortar: approximately 3 bags (25 kg) per m2 of wall. Grout: 0.25 liters per cell per course for 190 mm block. Rebar lap splice = 40 bar diameters per EN 1996 (Eurocode 6).
Reinforcement per EN 1996 (Eurocode 6)
Vertical rebar (8 to 20 mm B500B) placed in grouted cells at 200 to 1200 mm on center. Horizontal rebar (8 to 12 mm) in bond beam blocks at 200 to 1200 mm course spacing. Standard 6-meter bars with 40-diameter lap splices where needed.
Export & Save
Save calculations to the built-in history table and export results as formatted text, CSV spreadsheet, A4 portrait JPG image, or a single-page PDF with diagram and data. Choose from 10 currencies across the EU and EEA. All estimates are for planning purposes -- consult a licensed structural engineer for load-bearing applications.
