Example 1
- Area: 42 m²
- Consumption: 1.2 kg/m²
- Layers: 1
- Bag size: 20 kg
You need 50.4 kg of material
That equals 3 full bags
How many kg of plaster for 42 m²? 1.2 kg/m² × 1 coat → 50.4 kg (3 bags of 20 kg).
Plaster Calculator
Enter 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. Two coats on 65 m² at 1.0 kg/m² give 130 kg.
Results
Enter the area, consumption in kg/m², number of coats, and bag weight. The result appears below.
The plaster calculator turns area and unit consumption into kilograms and full bags. It also shows mass per coat, consumption used, and leftover in the last bag. Measure walls with the wall area calculator, then paint with the paint requirement calculator.
How the results are calculated
Area42 m²
Consumption1.2 kg/m²
Coats1
Mass50.4 kg
The plaster calculator counts kilograms and bags. Mass = area × consumption × coats. Alternatively consumption comes from plaster type times thickness in mm (gypsum ≈ 0.8 kg/m² per mm, cement ≈ 1.2). Bags = ⌈mass / bag size⌉. This is finish plaster, not mortar from a separate page.
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 coats 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 × 3 × 2.6 m are 36.4 m² on the wall area page.
Enter area, consumption in kg/m², and the number of coats. Bag size, thickness, type, and price are optional. If you enter type and thickness instead of consumption, the calculator computes kg/m². A comma in 1.2 works like 1.2.
Paint after plaster is on the paint-requirement page: 39.6 m² at 12 m²/L and two coats is 6.6 L. Mortar from layer thickness is on a separate page. Tile adhesive depends on the trowel notch and has its own calculator.
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. Enter 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.
How to use this calculator
- Enter area in the header unit, for example 42 m² from the walls or 18 m² from a bath.
- Enter consumption in kg/m² from the bag and the number of coats. Thickness and type are the alternative to consumption.
- Set bag size, for example 20 kg or 25 kg. Price per bag is optional.
- Click Calculate. 42 m², 1.2 kg/m², and 1 coat give 50.4 kg, 3 bags of 20 kg.
- Wall area and paint are in the related calculators. This one counts plaster alone.
Formula
mass = area × consumption_kg/m² × coats
consumption_kg/m² (alt.) = type_factor × thickness_mm
bags = ⌈ mass / bag_size ⌉
Gypsum ≈ 0.8 kg/m² per mm; cement ≈ 1.2 kg/m² per mm. At 42 m², 1.2 kg/m², and one coat: 42 × 1.2 × 1 = 50.4 kg. With a 20 kg bag: ⌈50.4 / 20⌉ = 3 bags. This is a shopping estimate, not a manufacturer sheet.
kg and m² on plaster
42 m² at 1.2 kg/m² and one coat is 50.4 kg, 3 bags of 20 kg. Two coats multiply mass in a straight line.
- m²
- Wall or ceiling area. 42 m² room, 65 m² with two coats, 36.4 m² from 4×3×2.6 m.
- kg/m²
- Bag consumption or type × mm. Gypsum ≈ 0.8 kg/m² per mm; cement ≈ 1.2.
- coats
- Mass multiplier. 65 × 1.0 × 2 = 130 kg.
- bag
- A full package. 50.4 kg at 20 kg is 3 bags after rounding up.
Example scenarios
Example 2
- Area: 65 m²
- Consumption: 1.0 kg/m²
- Layers: 2
- Bag size: 25 kg
You need 130.0 kg of material
That equals 6 full bags
65 m² × 1.0 kg/m² × 2 coats → 130 kg (6 bags of 25 kg).
Example 3
- Area: 18 m²
- Consumption: 1.5 kg/m²
- Layers: 1
- Bag size: 5 kg
You need 27.0 kg of material
That equals 6 full packs
18 m² × 1.5 kg/m² × 1 coat → 27 kg (6 packs of 5 kg).
Example 4
- Area: 16 m²
- Consumption: 0.9 kg/m²
- Layers: 1
- Bag size: 20 kg
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.
Example 5
- Area: 28 m²
- Consumption: 1.2 kg/m²
- Layers: 1
- Bag size: 20 kg
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.
Example 6
- Area: 12 m²
- Consumption: 1.5 kg/m²
- Layers: 2
- Bag size: 5 kg
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.
Example 7
- Area: 40 m²
- Consumption: 1.8 kg/m²
- Layers: 1
- Bag size: 25 kg
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.
Example 8
- Area: 32 m²
- Consumption: 1.0 kg/m²
- Layers: 2
- Bag size: 25 kg
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.
Related calculators
Frequently asked questions
How do I calculate plaster from area and kg/m²?
Multiply area by consumption in kg/m² and by the number of coats. 42 m² × 1.2 kg/m² × 1 → 50.4 kg. With a 20 kg bag that is 3 bags.
How many bags do I need for 42 m² at 1.2 kg/m² with a 20 kg bag?
3 bags. Mass 50.4 kg divided by 20 kg and rounded up. Two coats on 65 m² at 1.0 kg/m² give 130 kg.
Is this a drywall mud calculator in gallons by finish level?
No. This page reports kilograms from area, kg/m², and coats (then bags). US gallon charts by finish level are outside this tool.
How is plaster mass calculated?
The calculator multiplies area by consumption in kg/m² and by the number of coats. At 42 m², 1.2 kg/m², and one coat the mass is 50.4 kg. With a 20 kg bag that is 3 bags, because 50.4 / 20 rounds up.
Where does kg/m² consumption come from?
From the bag or the manufacturer sheet. Alternatively enter thickness in mm and a type: gypsum about 0.8 kg/m² per mm, cement about 1.2 kg/m² per mm. Use one consumption source at a time — either kg/m², or type with thickness.
How do coats and bags work?
Each coat multiplies mass in a straight line. Two coats on 65 m² at 1.0 kg/m² give 130 kg. Bags are ceil(mass / bag size). At 130 kg and a 25 kg bag the result is 6 bags.
Is a ceiling calculated like walls?
Yes. The formula is the same: area × consumption × coats. Ceilings are often harder to apply evenly, so the bag-rounding reserve is useful.
What if consumption and thickness are both empty?
Without consumption or a type+thickness pair there is no kg/m². Enter an area greater than zero and one consumption source in the header unit.
How is plaster different from mortar?
Plaster uses kg/m² and coats (or type and mm). Mortar uses bed thickness and density. They are separate calculators — do not mix them when buying.
Where do I calculate paint after plaster?
On the paint requirement page. At 39.6 m², 12 m²/L coverage, and two coats the result is 6.6 L. Wall area lives on the wall area page.
Does the result round bags up?
Yes. Stores sell full bags. 2.52 bags becomes 3. Leftover from the last bag usually covers corners and touch-ups.
How does price per bag work?
When you enter a price and a bag size, cost uses full bags: bag_count × price. Without a price the calculator shows only mass and bags.
Does the result replace the manufacturer sheet?
No. It is an estimate from the numbers you enter. Absorbent substrates, thicker coats, and repairs can raise usage. The calculator reports mass and bags.
Is this a free plaster calculator?
Yes. Enter area, kg/m², and coats and you see kilograms and bags at once. No account required.
Knowledge sources
Plaster mass follows from area and unit consumption. Below are mass and SI units. Bag consumption comes from the product technical sheet.
Page updated October 12, 2026.