About this calculator
This calculator works out how many skirting boards to buy for a room and how to cut them. Draw the room with the shape input (rectangle, L, T, U, alcove or your own rectangles), add the doorways, and enter the board's size and stock length.
The skirting length is the room's real perimeter minus the doorways. It is then cut wall by wall into real pieces — a doorway splits a wall into two pieces, and a wall longer than one board is joined — and those pieces are nested into stock lengths, so you get both the number of boards and a cutting plan that shows which piece comes from which board and what is left over.
Inside and outside corners are counted from the room shape. A mitred outside corner (e.g. the inner corner of an L-shaped room or a chimney breast) needs a piece one board thickness longer than the wall. If you use a skirting system with moulded corners, joiners and end caps, switch that on to count them instead.
Formula
net length = room perimeter − doorway widths
pieces = each wall's run(s) between corners and door jambs,
split into stock-length pieces where longer than a board
mitre allowance = + board thickness at each outside-corner end (mitred)
boards = first-fit-decreasing nesting of the pieces
+ waste % of the cut length, packed as extra length
offcut = boards × stock length − cut length
inside corners = corners of the room where skirting meets from both walls
outside corners = reflex corners (projecting walls) likewise
joiners = joints inside long walls (system accessories)
end caps = free ends at door jambs (system accessories)
clips / nails = ceil(rate per metre × net length)
cartridges = ceil(net length / metres per cartridge)
Worked example
A 5 × 4 m room, one 900 mm door starting 500 mm from wall 1's start corner, 2.5 m boards, 10 % waste, 2 clips per metre:
perimeter = 2 × (5000 + 4000) = 18 000 mm
net length = 18 000 − 900 = 17 100 mm
pieces = wall 1: 500, 2500 + 1100 wall 2: 2500 + 1500
wall 3: 2500 + 2500 wall 4: 2500 + 1500 → 9 pieces
boards = 8 nested without waste; with 1710 mm waste added → 9
offcut = 9 × 2500 − 17 100 = 5400 mm
corners = 4 inside, 0 outside
clips = ceil(2 × 17.1) = 35
FAQ
Why is the board count higher than the length divided by the stock length? Because boards cannot be joined anywhere you like: each wall needs its own pieces, and the 500 mm piece next to a door does not use up a 1100 mm offcut from somewhere else unless it fits. 17.1 m ÷ 2.5 m suggests 7 boards; the real cut list needs 8 before any waste.
How do I tell the calculator which wall a door is on? The walls are numbered on the drawing in order around the room. Pick the wall and enter the distance from that wall's start corner (the corner its number starts from, going around the room) to the door's edge.
What does the waste allowance cover? Saw cuts, a bad piece, a mitre that has to be recut. It is packed as extra length, so it adds boards only when the offcuts cannot absorb it. Soudal, for example, advises allowing about 10 % for sawing waste.
Where do the clips per metre come from? They are placeholders. The clip system's or adhesive's instructions give the real figure — enter it.
Are door frames or architraves included? No. Use the door trim calculator for architraves.
Assumptions and limits
No standard is cited: skirting quantities are a cut list, and no standard governs them.
Defaults to replace: 80 × 16 mm board, 2500 mm stock length, 10 % waste, 2 clips / 3 nails per metre, 8 m per adhesive cartridge, one 900 mm door.
Geometry: walls are straight and meet at right angles (the shape input only produces rectilinear rooms). Inside corners are cut to the wall length (mitred or scribed); outside corners are mitred and get one board thickness extra per piece. Joints inside long walls are butt or scarf joints with no extra length. Built-in furniture, radiator pipes and floor-level obstacles are not deducted. Offcuts from one wall are reused on another wherever the nesting can fit them.