Calculate the plaster quantity needed for walls and ceilings. Estimate cement, sand, plaster volume, cement bags and material cost from your project dimensions.
Project Dimensions
Enter the surface area and plaster thickness.
How the Plaster Calculator Works
The calculator first determines the surface area to be plastered. It subtracts any doors, windows or other openings entered in the optional openings field.
The net plaster area is multiplied by the selected plaster thickness to calculate the wet plaster volume. A dry volume factor then accounts for the extra material volume required when cement and sand are mixed.
The dry volume is divided according to the selected cement-to-sand ratio. The calculator then converts the cement volume into weight and estimates the number of cement bags required.
Plaster Mix Ratios
| Mix Ratio | Cement | Sand | Typical Use |
|---|---|---|---|
| 1:3 | 1 part | 3 parts | Stronger plastering applications |
| 1:4 | 1 part | 4 parts | General plastering |
| 1:5 | 1 part | 5 parts | General wall surfaces |
| 1:6 | 1 part | 6 parts | Common general-purpose estimate |
Plaster Quantity Formula
Plaster Area = Surface Length × Surface Height − Openings
Wet Volume = Plaster Area × Thickness
Dry Volume = Wet Volume × Dry Volume Factor
Cement Volume = Dry Volume × Cement Parts ÷ Total Mix Parts
Sand Volume = Dry Volume × Sand Parts ÷ Total Mix Parts
How Much Plaster Do You Need?
The amount depends mainly on the wall area, plaster thickness and mix ratio. A thicker plaster layer requires more material for the same surface area.
For example, increasing plaster thickness from 12 mm to 15 mm increases the plaster volume by 25% before the dry-volume and waste allowances are applied.
Important Construction Note
Plaster quantities are estimates. Actual material use varies with wall condition, surface unevenness, workmanship, material moisture, mixing method and site waste. Follow the project specification when a specified plaster mix or thickness is required.
Plaster Calculator FAQs
Multiply the plastered surface area by the required plaster thickness to find the wet plaster volume. Apply a dry-volume factor and waste allowance to estimate the cement and sand required.
The number of bags depends on plaster area, thickness, cement-to-sand ratio, cement density, bag size and waste allowance. Enter those values in the calculator for an estimate.
Common plaster mixes include 1:3, 1:4, 1:5 and 1:6 cement-to-sand ratios. The appropriate ratio depends on the surface, exposure and project specification.
Plaster thickness varies by surface and project requirements. Around 10 mm to 15 mm is common for many general wall applications, but the specified thickness should come from the project requirements.
Dry cement and sand occupy a different volume from the finished wet plaster. The dry volume factor provides an allowance for this change when estimating loose materials.
No. Enter their combined area in the openings field so the calculator subtracts it from the total surface area.