Overview
This calculator is built for plaster planning on façades, partition walls, ceilings, and renovation work where you need to know the material volume before ordering. It multiplies the surface area by the declared consumption per millimetre and by the planned thickness, then adds your waste allowance and converts the result into bags. Use it when you have product data in kg/m²/mm and want a realistic buying quantity rather than a theoretical minimum. If the substrate is rough, the wall is highly absorbent, or the application is split across several rooms, the waste field helps you avoid under-ordering.
Use cases
- Facade order for a villa wallEstimate the plaster load for an exterior wall before placing a material order, especially when the coating thickness follows a manufacturer specification.
- Interior renovation of a living roomWork out how many bags are needed for fresh interior plaster on several walls and a ceiling, including a small reserve for joints and corners.
- Rough substrate allowanceAdd extra material for masonry with uneven suction or repair patches so the purchase quantity reflects real site conditions.
- Comparing two plaster systemsCheck how bag count changes when a lighter or denser plaster has a different consumption rate at the same thickness.
How it works
- 1
Enter the area in square metres.
- 2
Set the consumption rate in kg/m²/mm from the product sheet.
- 3
Enter the planned layer thickness in millimetres.
- 4
Add a waste percentage for losses, unevenness, and leftovers.
- 5
Enter the bag weight in kilograms.
- 6
Review base kilograms, total kilograms with waste, and the number of bags.
Examples
Typical façade estimate
Input: Area: 120 m², consumption: 1.7 kg/m²/mm, thickness: 12 mm, waste: 8%, bag weight: 25 kg
Output: Base plaster: 2448 kg, total plaster: 2643.84 kg, bags needed: 105.75 → 106 bags
A realistic order check for an exterior façade with a modest reserve.
Room-by-room interior job
Input: Area: 38 m², consumption: 1.3 kg/m²/mm, thickness: 9 mm, waste: 6%, bag weight: 30 kg
Output: Base plaster: 444.6 kg, total plaster: 471.28 kg, bags needed: 15.71 → 16 bags
Useful for planning a small interior refurbishment with standard sacks.
Deep repair layer
Input: Area: 22 m², consumption: 2.0 kg/m²/mm, thickness: 15 mm, waste: 12%, bag weight: 20 kg
Output: Base plaster: 660 kg, total plaster: 739.2 kg, bags needed: 36.96 → 37 bags
Shows how thicker repair layers can raise the total sharply even on a small area.
FAQ
How is the final bag count calculated?
The tool multiplies area by consumption per mm and by thickness, then adds waste. That total is divided by the bag weight to show the number of bags.
Why can the result include decimals before rounding?
Decimals show the exact arithmetic result. In practice, you should buy whole bags and round up, because a partial bag cannot be purchased.
What if the product data is given per centimetre instead of per millimetre?
Convert it first. A value per centimetre must be divided by 10 to get kg/m²/mm, otherwise the result will be too high by a factor of ten.
Does the waste field mean leftover sacks or application losses?
It covers both. Use it for material left in the bucket, losses on rough corners, and extra demand from uneven walls.
Can I use it when the same room has different thicknesses?
Yes, but calculate each thickness separately and add the results. Using one average thickness can hide large differences in consumption.