Wall plaster and mortar calculator
Calculate the mortar for scratch coat, base coat and finish coat on walls: volume per layer, bags of cement, sand and lime from the mix, or bags of premixed mortar, with waste included.
Mortar for plastering walls
Scratch coat calculated with a 1:3 mix (cement and sand). Densities used: cement 1,400 kg/m³ (50 kg bag), hydrated lime 600 kg/m³ (20 kg bag). Estimate: confirm with your supplier.
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Wall plaster and mortar calculator: what it is for
Enter the wall area, whether one or both sides are plastered, the thickness of the scratch coat, base coat (or single coat) and finish coat, and the mix. The calculator shows the volume of each layer with waste, the bags of cement and lime and the cubic meters of sand from the mix, or the number of bags of premixed mortar from the manufacturer's usage.
The calculations run in your browser and are estimates; confirm the quantities with your supplier or a professional before buying.
How to use
- Enter the area and the thicknesses.
- Choose the mix or the premixed mortar usage.
- See the volume and the bags of material.
When to use it
- Budget the plastering of a renovation.
- Compare site-mixed and premixed mortar.
- Plan the purchase of cement and sand.
Frequently asked questions
What are the plaster layers?
The scratch coat is a thin, rough layer of about 5 mm that gives grip. The base coat levels the wall and is usually 1.5 to 2.5 cm. The finish coat is a thin layer of about 5 mm. Many jobs use a single coat of 2 to 2.5 cm that does the work of both base and finish.
How is the amount of material calculated from the mix?
The volume of wet mortar is multiplied by a factor of about 1.3 to get the dry volume, because the mix loses volume when water is added. That volume is divided by the parts of the mix: in a 1:2:8 mix, for example, 1 part is cement, 2 are lime and 8 are sand.
How far does premixed mortar go?
It depends on the brand, but common usage is 1.6 to 1.8 kg per m² for each millimeter of thickness. The calculator uses 1.7 kg/m²/mm and you can adjust it to the product's bag.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.