You need about 8.3 linear meters of deck board per m² with common 120 mm (4 3/4 in) wide boards – roughly 2.5 linear feet per square foot. The math is simple: 1000 mm divided by the board width in mm gives linear meters per square meter – 1000/120 ≈ 8.33. Narrower boards mean more linear length per m², wider boards less. Add about 10 % waste allowance before you order.
Here you get the full calculation, conversion tables for the most common board widths and deck sizes, and a complete worked example.
What does linear length mean?
Linear meters (or linear feet) measure the length of the material, regardless of width and thickness. Deck boards are often priced and sold per linear meter or linear foot, while you measure the deck in square meters or square feet. That makes the conversion from area to linear length the most important calculation in the whole materials plan.
Linear meters per m² by board width
| Board width | Calculation | Linear meters per m² |
|---|---|---|
| 95 mm (3 3/4 in) | 1000/95 | approx. 10.5 lm |
| 120 mm (4 3/4 in) | 1000/120 | approx. 8.3 lm |
| 145 mm (5 3/4 in) | 1000/145 | approx. 6.9 lm |
If you work in feet and inches, the same logic applies: 12 divided by the board width in inches gives linear feet per square foot. A 145 mm board is close to the actual width of a typical 5/4 × 6 deck board, which works out to roughly 2.1–2.2 linear feet per sq ft.
The formula 1000/board width assumes the board covers exactly its own width. In practice you lay the boards with a 3–5 mm (1/8–3/16 in) gap, so each row covers slightly more – the formula therefore gives you a small built-in margin. Which board width you should choose, and what it does to price and workload, is covered in how to choose deck board width.
Conversion table: m² to linear meters
Here is the requirement for common deck sizes, before waste:
| Area | 95 mm boards | 120 mm boards | 145 mm boards |
|---|---|---|---|
| 10 m² (108 sq ft) | approx. 105 lm | approx. 83 lm | approx. 69 lm |
| 15 m² (161 sq ft) | approx. 158 lm | approx. 125 lm | approx. 104 lm |
| 20 m² (215 sq ft) | approx. 211 lm | approx. 167 lm | approx. 138 lm |
| 30 m² (323 sq ft) | approx. 316 lm | approx. 250 lm | approx. 207 lm |
| 50 m² (538 sq ft) | approx. 527 lm | approx. 417 lm | approx. 345 lm |
Remember to add waste allowance to the numbers in the table before ordering – see below.
Worked example: a 20 m² deck
- Area: 5 m × 4 m = 20 m² (about 16.4 × 13.1 ft = 215 sq ft)
- Linear meters: 20 × 8.33 ≈ 167 lm (120 mm boards)
- Waste allowance: 167 × 1.10 ≈ 184 lm
- Number of boards: 184 / 4.2 m ≈ 44 boards at 4.2 m (about 14 ft)
Choose board lengths that suit the deck’s dimensions where you can – a deck that is exactly 4.2 m deep needs no butt joints if you buy 4.2 m boards.
Price per linear length makes comparison easier
Once you know your linear requirement, comparing prices also gets easier. Lumber yards often quote a price per linear meter or linear foot, while contractor quotes are often given per square meter or square foot. With the conversion above you can go both ways: a linear price of $2 per linear foot for a board covering about 2.5 linear feet per sq ft corresponds to roughly $5 per sq ft in material cost for the decking surface alone. That way you quickly see what is actually cheapest when different suppliers quote prices differently.
Remember waste allowance
End cuts, fitting around corners, and a few boards with defects are normal on every project. Add:
- about 10 % for an ordinary rectangular deck
- about 15 % for diagonal layouts, many angles, or a complex shape
Why the waste occurs, and how to make a simple cutting plan, is covered in deck board waste allowance.
Use the calculator
The calculator on this page does the whole conversion for you: enter the deck’s dimensions and board width, and you get linear length of decking and the number of screws (figure 35–40 screws per m², or 3–4 per sq ft). If you want to follow the whole path from estimate to order, read how to estimate deck boards using a calculator.
Frequently asked questions
How many linear meters of deck board per m²?
About 8.3 linear meters per m² with 120 mm (4 3/4 in) wide boards. With 95 mm boards you need about 10.5 lm, and with 145 mm boards about 6.9 lm per square meter.
How do I convert square meters to linear meters?
Multiply the area by 1000 divided by the board width in millimeters. Example with 25 m² and 120 mm boards: 25 × (1000/120) = 25 × 8.33 ≈ 208 linear meters. Then add about 10 % waste allowance.
How many linear feet of decking per square foot?
Divide 12 by the board width in inches. A typical 5/4 × 6 board (about 5 1/2 in actual width) gives roughly 2.2 linear feet per sq ft; a 120 mm (4 3/4 in) board gives about 2.5 linear feet per sq ft.
Should the gap between boards be included in the calculation?
With the formula 1000/board width, the practical answer is no: the 3–5 mm (1/8–3/16 in) gap means each row covers slightly more than the board width, so the formula gives you a small safety margin instead.
How much extra should I order?
Add about 10 % to the linear total for an ordinary deck, and about 15 % for diagonal layouts or lots of fitting. Always round up to whole board lengths as they are sold.