What are linear metres, and why does the contractor price in them?
A linear metre is length alone — no width, no height. Skirting boards, worktops and new partition walls are priced per metre, because the work follows the length, not the surface. So your takeoff needs both square metres and linear metres.
Short answer: a linear metre (abbreviated l.m. or lin. m) is a length measured in metres, where the width and height are fixed in advance and therefore are not multiplied in. A skirting board is sold per linear metre, because the profile is always the same — only the length varies. Contractors price in linear metres when the work follows a line — skirting, plinths, worktops, walls, sealant joints — and in square metres when the work covers a surface.
Linear metres, square metres and units — the three measures in a quote
Almost every line in a contractor's quote is one of three kinds. Learn to tell them apart, and you can read a quote and see what is missing.
- Square metres (m²) — work that covers a surface: painting walls and ceilings, flooring, plasterboard, tiling, insulation, filling.
- Linear metres (l.m.) — work that follows a line: skirting boards, quarter-round trim, worktops, sealant joints, plinths, new partition walls, guttering, fencing.
- Units (units) — work that repeats per item: fitting a door, a window reveal, a socket, a hinge, a door handle.
One and the same job typically contains all three. A painting job in a single living room is 33.8 m² of net wall plus 13.8 linear metres of skirting plus 3 units of reveals. Give the contractor only the m², and the other two have to be guessed.
Why the length is enough
A skirting board has a fixed profile — say 15 mm thick and 68 mm tall. However many metres you buy, the cross-section stays the same. So there is nothing to multiply by: the price is quoted per metre, and the labour is roughly proportional to the metres too.
The same goes for a kitchen worktop of a fixed depth, a sealant joint in a bathroom, guttering, or a new plasterboard partition wall of a fixed room height. As soon as height and width are fixed, length is the only thing that varies — and linear metres is the precise measure.
A sum you can follow
A room measuring 4.20 m by 3.60 m, with two 90 cm doors, and skirting that does not run behind the doors.
- Perimeter: (4.20 + 3.60) × 2 = 15.60 l.m.
- Deduction for two doorways: 2 × 0.90 = 1.80 l.m.
- Net skirting: 15.60 − 1.80 = 13.80 l.m.
- Waste allowance for cutting, typically 5-10 %: 13.80 × 1.10 = 15.2 l.m. to buy
Two things are worth noting. First: doors are deducted in linear metres, just as they are deducted from the net wall surface — but here it is the width that is deducted, not the area. Second: the number of corners costs time, even though it does not show up in the metres. Eight mitre cuts in a room with a recess is more work than four cuts in a rectangular room, and that is why a contractor asks about the room's shape, not only its perimeter.
The price per metre itself depends on the type of wood, the profile, and who is fitting it — that has to come from your own quote. The quantity, on the other hand, you can work out yourself, and it is the quantity that quotes need to be compared on.
Where linear metres typically turn up in a home
- Skirting boards and floor trim — the room's perimeter minus doorways.
- Transition strips in doorways — per door width, often priced per unit.
- Kitchen worktop — plus a surcharge per cut-out for sink and hob (units).
- Sealant joints in a bathroom — along every corner and transition; often more metres than you would think.
- New partition walls — per linear metre at a given room height, plus per unit for doorways.
- Window reveals — either linear metres along the three or four sides, or per unit per opening.
- Guttering, fascia boards, fencing and terrace edging outdoors.
The trap: linear metres in a room that is not a rectangle
The perimeter of a rectangular room is easy. If the room has a recess, a bay, a chimney breast or a splayed corner, the perimeter is longer than (length + width) × 2 — and the skirting follows the actual edge all the way round.
A recess 60 cm wide and 40 cm deep adds two lots of 40 cm, in and out — 0.80 l.m. extra — even though the room's overall dimensions are unchanged. Four such details, and you are three metres of skirting and eight extra mitre cuts short. That is the classic reason a skirting job ends up costing more than expected.
This is why a measured floor plan is worth more than two numbers. The perimeter can be read off the drawing's actual edge, not off a rectangle someone assumed.
How to write it in a quote request
Give both measures, and say which is which:
"Living room: 15.1 m² floor, 15.1 m² ceiling, 33.8 m² net wall (39.0 m² gross). Skirting: 13.8 l.m. net after deducting 2 doorways, 6 outward and 2 inward corners. Openings: 1 window 120×130 cm, 2 doors 90×204 cm."
A contractor can price that kind of line directly. The substrate still needs to be seen before the price can be fixed, but the quantities are worked out before the van sets off — and that is often the difference between getting a figure this week and getting it next week.
How to get both m² and linear metres without measuring twice
Measure by hand, and you get linear metres for free, if you measure each wall's length individually instead of only the room's two overall dimensions — it is the individual wall sections that are the linear metres, and it is between them that the corners are counted.
HouseSense works out both from the same geometry. Scan the home with LiDAR on an iPhone Pro — or draw it on the screen's squared paper — and the app knows every wall's actual length, not just the room's outer rectangle. The takeoff gives net wall surfaces with doors and windows deducted, floor and ceiling areas, ceiling heights, and a window and door schedule with every opening's size and position. Recesses, bays and out-of-square corners are all counted, because they are in the drawing itself.
Whichever method you use, the rule is the same: never give square metres alone. Half of a quote is priced in metres and units, and those figures have to come from somewhere.