Use our plaster coverage per bag calculator to find out how much area one bag of plaster covers. Supports metric & imperial units, plus cost calculation.
Enter your measurements above to see the results.
First, convert all inputs to a consistent unit system. For metric: areaPerBag = bagSize / (coverageRate * thickness). For imperial: convert thickness from inches to mm, bagSize from lb to kg, area from ft² to m², and coverageRate from lb/ft²/in to kg/m²/mm. Bags required = area / areaPerBag (rounded up). Total cost = bagsRequired * pricePerBag.
Suppose you have 25kg bags, want to plaster a 20m² wall at 12mm thickness, with a manufacturer's coverage rate of 1.5 kg/m²/mm and each bag costs £8.50. Area covered per bag = 25 / (1.5 * 12) = 1.39 m². Bags required = ceil(20 / 1.39) = 15. Total cost = 15 * £8.50 = £127.50.
Enter your bag size, desired plaster thickness, the total area to cover, and the manufacturer’s recommended coverage rate. Select your preferred unit system and currency. The calculator will show how much area each bag covers, how many bags you need, and the total cost.
Coverage depends on the plaster type, bag size, thickness applied, and the condition of your wall or ceiling. Always check the manufacturer’s guidance for accurate coverage rates. Applying plaster thicker than recommended will reduce coverage per bag.
Estimating plaster needs correctly helps prevent waste, saves money, and ensures you order enough material for a seamless finish. Overbuying leads to unnecessary cost, while underestimating can delay your project.
Material cost is only part of plastering expenses. Consider labour, preparation, and finishing costs when budgeting your project. This calculator helps you estimate the plaster material cost based on your local currency and price per bag.
For more detailed plastering calculations, try our Two Coat Plaster Calculator, Plaster Calculator, or Cement Plaster Mix Calculator. These tools help with different plastering scenarios and material mixes.
A standard 25kg bag of plaster typically covers around 10–12 m² at 2mm thickness, but this varies by plaster type and thickness. Use the calculator above for an exact estimate based on your specific details.
To find bags per m², divide 1 by the area covered per bag. For example, if one bag covers 10 m², you need 0.1 bags per m². The calculator does this for you based on your thickness and coverage rate.
Measure the length and height of your wall or ceiling, then multiply to get the area (length × height = area). Enter this area into the calculator to estimate plaster needs.
Coverage per bag decreases as you increase plaster thickness. For example, a 25kg bag covers more area at 2mm than at 12mm. The calculator adjusts coverage automatically for your chosen thickness.
Material cost per square foot or metre depends on plaster price, bag size, thickness, and coverage rate. Enter your values to see the total cost and cost per area for your project.
