Type the area and the bag consumption. The calculator multiplies area by kg/m² and coats, then divides by bag weight. A 42 m² room at 1.2 kg/m² and one coat is 50.4 kg, 3 bags of 20 kg.
This calculator converts surface area and material consumption into a practical result in kilograms and full bags. It is useful when planning purchases for skim coat, finishing plaster, or similar wall-finishing materials. Measure walls with the wall area calculator, then paint with the paint requirement calculator.
Area, Consumption (kg/m²), Number of layers and Bag size (kg). The result shows up here.
The plaster calculator counts kilograms and bags. Mass = area times consumption times the number of layers. Alternatively, consumption comes from plaster type times thickness in mm. Bags are ceil(mass divided by bag size). This is finish plaster or a similar skim, not the cement mortar on the mortar card.
A 42 m² living room at 1.2 kg/m² and one coat is 50.4 kg and 3 bags of 20 kg, because 50.4 / 20 rounds up. Two passes on 65 m² at 1.0 kg/m² are 130 kg and 6 bags of 25 kg. A small 18 m² bath at 1.5 kg/m² and 5 kg bags is 27 kg and 6 packs. Walls 4 by 3 by 2.6 m are 36.4 m² on wall area.
Type area, consumption in kg/m², and the number of layers. Bag size, thickness, type, and price are optional. If you type type and thickness instead of consumption, the calculator computes kg/m². A comma in 1.2 works like 1,2.
Paint after plaster: 39.6 m² at 12 m²/L and two coats is 6.6 L. Mortar 567 kg from a 15 mm bed is another calculator. Tile adhesive follows a trowel notch.
Bags round up. 2.52 bags is 3. A second coat multiplies mass in a straight line: 65 × 1.0 × 2 = 130. Empty consumption and empty thickness together will not make a mass. Type 42, 1.2, 1, and 20 kg, click Calculate, and match 50.4 kg and 3 bags.
Then 65, 1.0, and 2 at 25 kg: 130 kg and 6 bags. Finally 18 and 1.5 at 5 kg: 27 kg and 6 packs.
42 m² at 1.2 kg/m² and one coat is 50.4 kg, 3 bags of 20 kg. Two coats multiply the mass.
You need 50.4 kg of material
That equals 3 full bags
This is a good example of a basic wall refresh before painting. In practice, buying full bags is normal, and the rounding margin is often useful for touch-ups.
You need 130.0 kg of material
That equals 6 full bags
With two layers, material usage grows quickly. A result like this helps avoid the common problem of running short near the end of the job.
You need 27.0 kg of material
That equals 6 full packs
For small jobs, smaller packs can be convenient, but the unit cost is often higher than with larger bags.
You need 14.4 kg of material
That equals 1 full bag
How much skim plaster for a 16 m² ceiling at 0.9 kg/m²? You need 14.4 kg of material, That equals 1 full bag.
You need 33.6 kg of material
That equals 2 full bags
How much gypsum plaster for 28 m² of kitchen walls? You need 33.6 kg of material, That equals 2 full bags.
You need 36.0 kg of material
That equals 8 full packs
How much plaster for two coats on a 12 m² hallway? You need 36.0 kg of material, That equals 8 full packs.
You need 72.0 kg of material
That equals 3 full bags
How much cement plaster for 40 m² of garage walls? You need 72.0 kg of material, That equals 3 full bags.
You need 64.0 kg of material
That equals 3 full bags
How much plaster for two coats on 32 m² of bedroom walls? You need 64.0 kg of material, That equals 3 full bags.
You get 50.4 kg. With a 20 kg bag that is 3 full bags, because 50.4 / 20 rounds up.
6 bags. Mass 130 kg, 130 / 25 = 5.2, rounded up to 6. Two passes double the kilograms.
6 packs. Mass is 27 kg, 27 / 5 = 5.4, so the calculator goes up to six.
From wall area. A 4×3×2.6 m room is 36.4 m² with no openings, close to that order.
Yes, at the same consumption. 42 × 1.2 × 2 = 100.8 kg, 6 bags of 20 kg.
Plaster type times thickness when you use those fields instead of kg/m². One consumption source at a time.
On paint requirement. 39.6 m² at 12 m²/L and two coats is 6.6 L.
Round up to 3. Leftover at corners and touch-ups eats a fraction of a bag.
Mortar uses bed thickness and density. Plaster uses kg/m² and coats. Two cards.
43.68 kg, so 3 bags of 20 kg, because 2.18 bags round up. Same 1.2 kg/m² as the 42 m² room.
Volume and waste come from the sizes you type. Below are volume and NIST SI units.
Page updated in 2026.
