Surface Areas
Quick answer: The walls of a 4 × 5 m room with 2.6 m ceilings measure 46.8 m², or about 43.3 m² net after subtracting the door and window.
Calculate wall and floor areas
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Guides for this job
How the calculation works
Pick a shape (rectangle, circle, triangle, trapezoid and others) or rooms with walls and openings, enter the dimensions and get the area in several units. For rooms the net wall area excludes doors and windows.
Formula and assumptions
Rectangle = a × b; circle = π × r²; triangle = ½ × base × height. Room walls = perimeter × height − openings (net, never below 0). Conversions: 1 m² = 10,000 cm² = 1,000,000 mm². Results are rounded only for display.
Worked example
Room 4 × 5 m, height 2.6 m: walls 2 × (4 + 5) × 2.6 = 46.8 m². Door 0.9 × 2.05 = 1.845 m² and window 1.2 × 1.4 = 1.68 m² → net 46.8 − 1.845 − 1.68 = 43.275 m² ≈ 43.28 m².
More worked examples
- Circular terrace of radius 1.5 m: π × 1.5² = 7.07 m².
- Gable wall: rectangle 6 × 2.5 m = 15 m² plus a triangle with base 6 m and height 2.4 m = ½ × 6 × 2.4 = 7.2 m², total 22.2 m².
Room 2.6 m high (floor and walls without openings)
| Room (m) | Floor area (m²) | Wall area (m²) |
|---|---|---|
| 3 × 3 | 9 | 31.2 |
| 3 × 4 | 12 | 36.4 |
| 4 × 5 | 20 | 46.8 |
| 5 × 6 | 30 | 57.2 |
| 6 × 8 | 48 | 72.8 |
What affects real consumption
- Measurement accuracy and uneven walls.
- Niches, columns and slopes that need measuring separately.
- Units: check whether the input is in m, cm or feet.
Common mistakes
- Forgetting to subtract doors and windows from the wall area.
- Mixing units, e.g. one side in cm and another in m.
- Measuring an irregular room as one rectangle instead of splitting it into simple shapes.
Frequently asked questions
Does the calculator also give ceiling and floor area?
For rooms you can include the ceiling, and the floor has the same area as the ceiling (length × width).
How are doors and windows subtracted?
Enter openings with their dimensions; their area is subtracted from the wall area.
How do I convert m² to ft²?
Multiply by 10.764; 1 m² ≈ 10.764 ft². The calculator shows several units at once.
How do I measure an irregular room?
Split it into rectangles and triangles, calculate each area and add them up; for niches or columns, subtract their area.
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Publisher: Art-Visum d.o.o. · Content reviewed:
Calculations use common consumption rates and manufacturers' technical data sheets; results are estimates. Methodology · Standards · About