Room Area Calculator
Floor, ceiling, walls, skirting and volume, all at once.
Inputs
Result
Formula
| Floor / ceiling | A = length × width |
| Perimeter | P = 2 × (length + width) |
| Gross wall area | A = P × clear height |
| Net wall area | A = gross − openings |
| Skirting | L = P − total door width |
| Volume | V = length × width × clear height |
A 6 × 4 m room at 2.8 m clear height with 4 m² of openings and a 0.9 m door: 24.00 m² floor and ceiling, 52.00 m² of net wall, 19.10 m of skirting, 67.20 m³ of volume and a wall-to-floor ratio of 2.17.
FAQ
Why not just multiply floor area by 3 for walls?
The “times 3” rule is a fit-out shortcut that only holds for roughly square rooms at 2.7-2.8 m. The longer the room, the worse it gets: a 6 × 4 m room has a wall-to-floor ratio of 2.17 while 3 × 8 m gives 1.83 — nearly 20% apart. Wall area drives paint and filler quantities, and running short mid-job risks a colour mismatch.
Should openings be deducted?
Yes for finishes such as paint, wallpaper and wall tiles. For filler and primer either is accepted and most estimators leave them in as margin. But the reveals — the inside faces of the opening — must be added: a 1.5 × 1.5 m window in a 200 mm wall has about 1.2 m² of reveal, so four windows is close to 5 m² that is easily forgotten.
How do clear height and storey height differ?
Storey height runs between structural floors; clear height runs from finished floor to underside of ceiling, the difference being slab thickness plus floor build-up. A 3.0 m storey usually gives 2.7-2.8 m clear. Wall areas must use clear height — using storey height overstates by about 10%, two extra tubs of paint across ten rooms.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.