Plaster Quantity Calculator
Calculate cement and sand needed for wall plastering.
Assumptions used in this calculation
- Dry volume factor: Uses a standard 1.33× bulking allowance for wet-to-dry mortar volume conversion.
About this calculator
Plastering material orders based on wet volume alone consistently fall short, because dry cement and sand shrink in volume once mixed with water and applied, and that shrinkage factor is easy to overlook when estimating by eye. This calculator multiplies wall area by plaster thickness to get wet mortar volume, applies a standard 1.33× dry volume factor to account for the compaction that happens during mixing, then splits that dry volume into cement bags and sand quantity using a standard mix ratio. Enter just the wall area and thickness, and it returns a buy-ready material list instead of you working through the wet-to-dry conversion and mix-ratio split separately. Because it treats any flat surface the same way internally, the same inputs and formula work equally well for a ceiling as for a vertical wall, just enter the ceiling's area in the wall area field.
Worked example
50 sqm wall, 12mm thick, 1:4 mix
Result: 5 cement bags needed
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