Mortar Calculator
Choose brickwork or plastering, enter area and thickness, and get mortar volume plus cement and sand quantities.
Inputs
Result
Formula
| Plastering | V = area × thickness ÷ 1000 × 1.05 (uneven substrate) |
| Brickwork | V = masonry volume × 0.26 |
| With waste | V_total = V × (1 + waste %) |
| Cement | W = V_total × kg per m³ (M5 200 / M7.5 230 / M10 275 / M15 330) |
| Sand | V_sand = V_total × 1.02 |
100 m² of plaster at 20 mm: 2.1 m³ net, 2.21 m³ with 5% waste, needing about 508 kg of cement (11 bags) and 2.25 m³ of sand for M7.5.
FAQ
Why is brickwork mortar estimated at 26% of masonry volume?
That is the void ratio of standard brickwork. One cubic metre holds about 508 bricks occupying 0.74 m³, leaving 0.26 m³ of mortar in the joints. With perforated bricks or AAC blocks that drops to 10-15%.
Why multiply plaster area by 1.05?
Because substrates are never perfectly flat. Permitted deviation is 4-5 mm, and hollows need extra mortar, so add 5% on top of the theoretical thickness, or 10% for uneven older walls.
Which grade should I use, M5, M7.5 or M10?
Brickwork: M10-M15 below ground level, M7.5-M10 for load-bearing walls, M5 for partitions. Plastering: M5-M7.5 indoors, M10 or above outdoors and in wet areas. Over-specifying wastes cement and increases shrinkage cracking.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.