Linear Metre Calculator — Convert m² to Linear Metres
Convert square metres (m²) to linear metres from effective material cover width, with an editable cutting allowance. Free UK linear metre calculator.
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How to convert square metres to linear metres
When a material covers a fixed width, divide the area in square metres by the material’s effective cover width in metres. The result is the linear metres needed before any cutting or selection allowance.
Linear metres incl. allowance = net linear metres × (1 + allowance %)
Worked example: 20 m² at 150 mm cover width
What does effective cover width mean?
Effective cover width is the amount of surface covered by one metre length of installed material. It can be less than the product’s overall manufactured width when boards, sheets or profiles overlap, interlock or conceal part of each other.
Use the installed cover width from the actual product data where possible. Entering overall width instead of effective cover width can understate the quantity required.
Common uses for a linear metre calculation
Cladding & boarding
Useful where a board or profile has a known effective face or cover width. Check laps, tongue-and-groove engagement and manufacturer coverage.
Decking & timber
Linear metres can help with early quantity planning, but dedicated decking tools are better where board gaps, stock lengths and joist spacing matter.
Sheet/profile systems
Use only where the product is genuinely ordered or estimated by run length at a fixed cover width. Sheet counts and panel modules may need a different method.
Linear metres are not square metres
Linear metres measure length. Square metres measure area. You can only convert between them when you also know a width. That width is why this calculator asks for effective cover width rather than pretending there is a universal m²-to-linear-metre conversion.
If you only need to calculate the area first, use the Floor Area Calculator or Wall Area Calculator.
How to enter cover width correctly
The calculator expects metres. Convert millimetres before entering them: divide mm by 1,000. For example, 95 mm = 0.095 m, 125 mm = 0.125 m and 150 mm = 0.15 m. Use the Builder Length Converter if you need help converting the product width.
Common linear-metre estimating mistakes
- Entering the overall product width when the installed cover width is smaller.
- Entering 150 mm as 150 m instead of 0.15 m.
- Assuming square metres can be converted to linear metres without knowing a width.
- Adding a waste allowance twice — once to area and again to the linear-metre result.
- Ordering the exact calculated run without checking the supplier’s stock lengths, pack quantities or minimum order.
From linear metres to a real material order
The calculated run is a planning quantity, not necessarily the final number of boards or stock lengths. After calculating the linear metres, check the product’s standard length, pack quantity, cutting layout and whether offcuts can be reused. For timber-specific planning, the Timber Length Calculator, Decking Board Calculator and Skirting Board Calculator may give a more useful order quantity.
Planning estimate only. Use the effective installed cover width and purchasing format for the exact product you intend to buy.
Frequently asked questions
How do I convert m² to linear metres?
Divide the area in square metres by the effective material cover width in metres. For example, 20 m² ÷ 0.15 m = 133.33 linear metres.
Can you convert square metres to linear metres without a width?
No. Square metres measure area and linear metres measure length, so a width is required to convert between them.
What is effective cover width?
It is the installed width that one run of material actually covers. It may be less than the overall product width because of overlaps or interlocking joints.
How do I convert a cover width in millimetres to metres?
Divide the millimetre value by 1,000. For example, 150 mm = 0.15 m.
Should I add a cutting allowance?
That depends on the material and layout. Keep the allowance explicit and editable, then check product guidance and stock lengths before ordering.
Can I use this for cladding or decking?
Yes for an early run-length estimate when you know the effective cover width. Dedicated material calculators are better when board gaps, laps, modules or stock lengths need to be modelled.
Related measuring tools
For area calculations, use the Floor Area Calculator or Wall Area Calculator. For other conversions, return to the Measuring & Conversions hub.