# Wall Plastering Quantity Calculator

> Estimate cement bags and sand for cement-sand plaster from the wall area, openings, plaster thickness, mix ratio and a dry-volume factor.

Category: Construction · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/wall-plastering-quantity-calculator

Plaster volume is the net wall area times the thickness. Scale it up for uneven surfaces and dry bulk, then split it by the cement-to-sand ratio.

Also called: Plastering material calculator, Rendering calculator.

## Inputs
- Units (options: Metric, Imperial; default metric)
- Wall length (default 5)
- Wall height (default 3)
- Doors and windows (total area) (default 3; optional)
- Plaster thickness (default 12)
- Cement parts (default 1)
- Sand parts (default 4)
- Dry-volume factor (default 1.27)
- Cement bulk density (unit kg/m³; default 1440)
- Cement bag size (unit kg; default 50)
- Waste allowance (unit %; default 10; optional)

## Results
- Cement bags (rounded up)
- Cement
- Sand
- Sand
- Plastered area
- Plastered area
- Wet plaster volume
- Dry material volume

## Formula

```
Area = L × H − Openings;  Wet = Area × t;  Dry = Wet × (1 + Waste) × Dry factor;  Cement = Dry × c ÷ (c + s) × density;  Sand = Dry × s ÷ (c + s)
```

Where:
- t: plaster thickness
- c : s: cement-to-sand ratio

## Worked example
1. Area = 5 × 3 − 3 = 12 m²; wet volume = 12 × 0.012 = 0.144 m³.
2. Dry volume = 0.144 × 1.10 × 1.27 = 0.2012 m³.
3. Cement = 0.2012 × 1/5 × 1440 = 57.9 kg → 2 bags of 50 kg; sand = 0.2012 × 4/5 = 0.161 m³.

**Result:** Plastering 12 m² at 12 mm in 1:4 takes about 58 kg of cement (2 bags) and 0.16 m³ of sand.

## What the result means

Plaster both faces of a wall by doubling the area. Rough brickwork or block takes more than smooth concrete, so raise the waste allowance for poor backgrounds.

## Assumptions and limits
- Uniform thickness over the whole area.
- Cement-sand plaster; gypsum and lime plasters are batched differently.
- Reveals, beads and ceiling work are not itemised.

## Questions

### Why add a waste allowance as well as the dry factor?

The dry factor converts wet to dry volume; the allowance covers material that fills hollows in the wall and drops to the floor.

### How thick should plaster be?

Commonly 12 mm on internal brick walls and 15–20 mm in two coats outside, but follow your specification.

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_Quantities are estimates. Confirm requirements with your engineer or supplier before ordering materials._

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/wall-plastering-quantity-calculator