Plaster Calculator
About the Plaster Calculator
Estimate the cement and sand needed to plaster a wall. Enter the wall area, the plaster thickness and the mix ratio, and the calculator returns the quantities of each material so you can buy the right amount and waste less on site.
This tool works in your browser: the files and text you use are processed on your device and are not uploaded.
How to use it
- Enter the plaster area in square feet.
- Set the plaster thickness in millimetres (12–15 mm is common internally).
- Choose the cement:sand ratio and read the cement bags and sand volume.
Frequently asked questions
What thickness should plaster be?
Internal walls are typically plastered 12–15 mm thick, while rough external faces often use 20 mm, sometimes in two coats. Thicker plaster uses proportionally more material.
What is a good cement-to-sand ratio for plastering?
1:4 to 1:6 is common. A richer 1:3–1:4 mix is used for external and structural surfaces, while 1:5–1:6 suits internal walls. Richer mixes are stronger but more prone to shrinkage cracks if over-troweled.
How is the cement quantity worked out?
Wet plaster volume = area × thickness; dry mortar is about 1.27× that. Cement’s share is 1/(1+sand parts) of the dry volume, converted to 50 kg bags using a cement density of ~1440 kg/m³.