Room renovation calculator
Renovating one room means several different sums over the same measurements. Here you enter the dimensions once — length, width, height and the openings — then tick what you are doing, and the calculator lists the quantity for each job: laminate square metres with waste, litres of paint, plasterboard sheets and metres of skirting. Every line leads to the detailed calculator for that material, which adds packs, tins and prices.
How the quantities are produced
floor = length × widthperimeter = 2 × (length + width)gross walls = perimeter × heightnet walls = gross − openings
The geometry is computed once. The openings you enter — doors and windows — come off the gross walls, and everything after that hangs on two numbers: the floor area and the net wall area.
The quantities then come from the same engines that drive the individual calculators: laminate adds waste to the floor area, paint multiplies the walls by the number of coats and divides by coverage, plasterboard divides the ceiling by the board's area, and skirting takes the door widths off the perimeter. That is why the figure here and the figure on the detailed calculator never drift apart.
The 10 % floor waste and the 10 m²/L coverage are starting values, not a rule — both fields stay editable, and for paint the coverage printed on your own tin always wins.
Example: a 4.2 × 3.6 × 2.5 m room
The room has one 0.9 × 2.05 m door and one 1.6 × 1.4 m window. The floor is 15.12 m², the perimeter 15.6 m, the gross walls 39 m² and the openings 4.085 m² — leaving 34.92 m² of wall to paint.
From those two numbers the list reads: 16.63 m² of laminate at 10 % waste, 7.68 L of paint for two coats at 10 m²/L, six 120 × 250 cm boards for the ceiling, and 14.7 m of skirting (the perimeter less the door width).
Tiles are shown as square metres with waste, but the piece count needs a tile size and the roll count needs the roll's own size — so those two lines send you to their own calculators instead of guessing.
What this page does not do
It does not price anything. Square metres and litres are the same in every shop; prices are not, so cost stays on the detailed calculators, where you also get packs.
It does not know your product. A 120 × 250 cm board, 10 % waste and 10 m²/L are starting points for an estimate; the label on your packaging always takes precedence.
It does not measure for you. If the room is not rectangular, split it into rectangles and add the areas, and treat sloping ceilings and alcoves separately.
Frequently asked questions
Why is skirting measured from the perimeter rather than the walls?
Skirting runs along the floor, so the room's perimeter is what counts. The total width of the doors you entered as openings comes off it — in the example 15.6 − 0.9 = 14.7 m. A doorway is the one place with no skirting.
Are the openings deducted from the laminate too?
No. Doors and windows are in the wall, so they only come off the walls. The floor stays length × width; if built-in units take up floor space, deduct them in the laminate calculator.
Why is there no piece count for tiles?
The piece count depends on the tile's format, and a room does not know it. The square metres with waste appear immediately, and the tile calculator gives pieces and boxes as soon as you enter the tile size.
Can I calculate several identical rooms at once?
Yes — the „number of identical rooms“ field multiplies every area. Openings are entered per room and multiplied by the same number, exactly as in the area calculator.