Concrete Block Calculator

Block count is wall area divided by the bonded face of one block - a 40 × 20 cm face with a 10 mm joint covers 0.081 m², giving 12.4-12.5 blocks per m². In imperial, an 8 × 16 face yields 1.125 blocks per ft². Mortar for standard 3/8 in (10 mm) joints runs about 3 bags of 80 lb (36 kg) masonry mix per 100 blocks, so a 40 m² wall at 500 blocks consumes roughly 15-16 bags. Worked example: 40 m² of wall × 12.5 = 500 blocks; add 5% waste (525 total) with 16 bags of mortar and 0.9 m³ of fill if you grout the cores at 1.2 m centers. Fill cores with concrete wherever rebar steps up the wall.

1. 1

   Measure the space

   Record the wall area and block size at the widest and longest points.

2. 2

   Enter the values

   Type the measurements into the calculator and select your units.

3. 3

   Apply the formula

   The tool computes Blocks = (Wall Area ÷ Block Face Area) × (1 + Waste %) for your inputs instantly.

4. 4

   Add waste and order

   Review the total with a 5-10% margin and round up to whole units.

• Wrong unit count per area

• Mortar joints of uneven width

• Dry absorbing units