Calculating Number of Blocks, simple and accurate method Before block work starts, you should know how many blocks you need. This saves money, reduces waste, and helps planning. Step 1. Measure the wall Calculate the wall area Wall length × wall height = wall area in m² Step 2. Know the block size Standard block face size is 450 mm × 225 mm That equals 0.45 m × 0.225 m Area of one block face 0.45 × 0.225 = 0.10125 m² Step 3. Calculate number of blocks Number of blocks = Wall area ÷ Area of one b