Example 1
- Length: 4 m
- Width: 3 m
- Height: 2.6 m
Wall area: 36.4 m²
This is a simple starting point for painting or estimating finishing materials in a small room.
Wall area calculator
Type room length, width, and height. This formula uses 2×(length plus width) times height and subtracts windows and doors. A 4 by 3 m room at 2.6 m is 36.4 m². A 5 by 4 m room at 2.7 m minus 4.5 m² openings is 44.1 m² net, the number you paste into paint.
This calculator quickly estimates wall area for painting, skim coat, wallpaper, or other finishing work. The result can be reduced by openings to better reflect the real material requirement. Calculate paint with the paint requirement calculator, plaster with the plaster requirement calculator, and bricks with the brick requirement calculator.
Results
Length, width, height, and windows. Wall area shows up here.
How the results are calculated
Wall area counts square meters for paint, plaster, or wallpaper. The formula is 2×(length plus width) times height, optionally plus length times width when you include the ceiling, minus windows, doors, and extra openings. Door height is fixed at 2.0 m. Window and door width and height use centimeters.
A 4 by 3 m room at 2.6 m with no openings is 36.4 m², one paint job. A 5 by 4 m living room at 2.7 m minus 4.5 m² openings is 44.1 m² net. A larger 6 by 4.5 m room at 2.8 m minus 5.2 m² is 53.6 m². Paint for 39.6 m² at 12 m²/L and two coats is 6.6 L on the next card.
Type length, width, and height in the header unit. Windows and doors are optional: count, width in cm, window height in cm. Extra openings in m² and the ceiling checkbox stay empty when you only want walls. A comma and a period are the same height, 2.6 and 2,6.
Paint liters from this area live on paint requirement. Plaster on 42 m² at 1.2 kg/m² is 50.4 kg and 3 bags of 20 kg. Floor area 5 by 4 m is 20 m², a different formula, with no wall height.
A 150 by 120 cm window is 1.8 m², which you subtract before you buy paint. Empty window fields deduct nothing. The ceiling adds floor area to the walls; leave it off when you only paint the verticals.
Type 4, 3, and 2.6, click Calculate, and match 36.4 m². Then 5, 4, 2.7 and 4.5 m² openings: 44.1 m² net.
How to use this calculator
- Type length, width, and height in the header unit, for example 4, 3, and 2.6.
- Optionally enter window and door counts and their width in centimeters. Door height is 2.0 m.
- Extra openings in m² and the ceiling box only when you need them.
- Click Calculate. 4×3×2.6 m is 36.4 m². 5×4×2.7 m minus 4.5 m² is 44.1 m² net.
- Paint and plaster use this area on their pages. This calculator stays wall m².
m² of walls in a 4 by 3 m room
2×(length plus width) times height, minus openings. A 4 by 3 m room at 2.6 m is 36.4 m².
- m²
- Wall area. 2×(4+3)×2.6 = 36.4. A 5 by 4 m room at 2.7 m minus 4.5 m² openings is 44.1 m² net.
- net
- After windows and doors. 44.1 m² from the second example pastes into paint, not the empty 36.4 from 4 by 3 m.
Example scenarios
Example 2
- Length: 5 m
- Width: 4 m
- Height: 2.7 m
- Openings: 4.5 m²
Net wall area: 44.1 m²
Subtracting openings gives a more realistic purchasing estimate, especially for paint, skim coat, and wallpaper.
Example 3
- Length: 6 m
- Width: 4.5 m
- Height: 2.8 m
- Openings: 5.2 m²
Net wall area: 53.6 m²
In larger rooms, even a small input error can easily change the result by several square meters.
Example 4
- 2.4 × 1.6 × 2.5 m
- 1 window 60×90 cm
- 1 door 80 cm
17.86 m²
How many m² of walls in a 2.4×1.6 m bathroom at 2.5 m with a window and a door? 17.86 m².
Example 5
- 3.8 × 3.2 × 2.6 m
- 1 window 90×120 cm
- 1 door 80 cm
33.72 m²
How many m² of walls in a 3.8×3.2 m kitchen at 2.6 m with a window and a door? 33.72 m².
Example 6
- 6.5 × 4.2 × 2.7 m
- 2 windows 140×140 cm
- 1 door 90 cm
- ceiling on
79.36 m²
How many m² of walls and ceiling in a 6.5×4.2 m living room at 2.7 m? 79.36 m².
Example 7
- 7.2 × 1.15 × 2.5 m
- 2 doors 80 cm
38.55 m²
How many m² of walls in a 7.2×1.15 m hallway at 2.5 m with two doors? 38.55 m².
Example 8
- 6 × 3.5 × 2.4 m
- 1 window 80×100 cm
- 1 door 240 cm
40.00 m²
How many m² of walls in a 6×3.5 m garage at 2.4 m with a wide door? 40.00 m².
Related calculators
FAQ
How many m² of walls in a 4×3×2.6 m room?
36.4 m². 2×(4+3)×2.6 = 36.4, with no openings and no ceiling.
How much net at 5×4×2.7 m and 4.5 m² openings?
44.1 m². Four walls are 48.6 m², then you subtract 4.5 m² of openings.
How much paint for 39.6 m² at 12 m²/L and two coats?
6.6 L on the paint calculator, three 2.5 L cans. This page stays wall area.
How do I type a 150 by 120 cm window?
Width 150 and height 120 in the centimeter fields, plus the window count. That is 1.8 m² to deduct.
Do doors have their own height?
The calculator uses 2.0 m. You type the door count and width in cm.
When do I include the ceiling?
When you also paint or plaster the ceiling. Length times width is added to the walls. For vertical walls only, leave the box off.
How much plaster for 42 m² at 1.2 kg/m²?
50.4 kg, 3 bags of 20 kg on the plaster page. Wall area only gives m².
How much net at 6×4.5×2.8 m and 5.2 m² openings?
53.6 m². That is the third card: 58.8 m² of walls minus 5.2 m².
Is 20 m² of floor the same as these walls?
No. 5 by 4 m is 20 m² of floor. Walls still need height: at 2.5 m that is 45 m² with no openings.
Do empty windows deduct zero?
Empty window and door fields deduct nothing. Leave extra openings empty when you have none.
Knowledge sources
Volume and waste come from the sizes you type. Below are volume and NIST SI units.
Page updated in 2026.