Easily work out how much plaster you need for two coat plastering. Calculate material quantities & total cost for any wall or ceiling area, metric & imperial.
Enter your measurements above to see the results.
First, convert thicknesses to metres or feet depending on unit system. Calculate total thickness (base plus finish). Multiply area by total thickness to get plaster volume. Convert to litres or US gallons. Divide area by the coverage per bag to get bags needed, rounding up. Multiply bags needed by price per bag for total cost.
Inputs: Unit system: Metric; Area: 25 m²; Base coat thickness: 10 mm; Finish coat thickness: 2 mm; Coverage per bag: 10 m² at total thickness; Bag size: 25 kg; Currency: GBP; Price per bag: 8. Calculation: Total thickness = 10 + 2 = 12 mm = 0.012 m; Total volume = 25 × 0.012 × 1000 = 300 litres; Bags needed = ceil(25 / 10) = 3; Total cost = 3 × £8 = £24.
To estimate plaster for two coats, add the base and finish coat thicknesses, then multiply by the total area to get the required volume. Divide the area by your selected plaster bag’s coverage to find the number of bags needed. Always round up to ensure you have enough material.
Two coat plastering involves applying a thicker base coat for levelling, followed by a thinner finish coat for a smooth surface. This method improves durability and finish quality compared to one coat systems, especially on uneven or masonry backgrounds.
A common approach is a 10 mm base coat and a 2 mm finish coat, but thickness can vary depending on wall condition and project requirements. Always check manufacturer guidelines or local standards for best results.
Coverage per bag depends on total thickness and product type. Most 25 kg bags cover about 10 m² at 12 mm combined thickness. Enter your specific bag details for an accurate calculation.
This calculator multiplies the number of bags needed by your plaster price per bag, giving a clear total cost in your chosen currency. Always allow for a little extra material to cover wastage or repairs.
Add both base and finish coat thicknesses, multiply by the total area, and divide by the coverage per bag. This calculator does it for you—just enter your figures.
Measure the wall area, add together the thickness of both coats, and multiply to get the total plaster volume. Divide by your bag’s coverage for the number of bags needed.
For a typical 10 mm base and 2 mm finish coat (total 12 mm), you’ll need about 12 litres of plaster per m². Adjust according to your actual thicknesses.
Plasterboard usually needs just a single skim coat, but two coat plastering is used on masonry or uneven surfaces for better finish and durability.
Allow the base coat to firm up and partially dry—typically 2–4 hours—before applying the finish coat. Always check your plaster’s manufacturer instructions.
