ToolnozaFormula for concrete block fill
Grout volume (m³) = block count × filled core volume per block (L) ÷ 1,000 × (1 + waste percentage ÷ 100). Use the volume for the cores that will actually be filled, not the block’s outside dimensions.
Example: 100 blocks with 10% allowance
If each block requires 4 L of grout in the specified cells, 100 blocks need 400 L before waste. Add 10%: 400 × 1.10 = 440 L, or 0.44 m³. Toolnoza’s calculator uses block count, filled core volume and waste percentage.
Get the correct core volume
Hollow blocks vary by size, core shape and manufacturer. Use the manufacturer’s technical data or project specification for the fill volume per block. If only selected cells are grouted, calculate the average volume for those blocks rather than assuming every core is filled.
Allow for reinforcement and site conditions
Waste depends on handling, spillage, delivery method and site conditions. Reinforcing bars displace some grout, while overfilling, uneven courses and leakage can increase use. The estimate is for material planning; it does not design the wall, specify grout strength or replace structural drawings.
Frequently asked questions
How many litres are in a cubic metre? 1,000. Should I use block outside volume? No; use the volume of cores to be filled. Does the result include mortar joints or the whole wall? No, it estimates core fill only; mortar, lintels and other materials are separate.