Why decking is bought in linear metres
Decks are planned in square metres of area, but hardwood decking is sold by the linear metre: the total length of board you buy. Converting between the two is the step most people get wrong, and getting it wrong either strands you short mid-job or leaves expensive hardwood in the shed. This guide shows the working; the timber calculator does it for you and shows the same working on screen.
Step 1: Measure your deck area
Measure the length and width of the deck surface in metres and multiply them for the area in square metres. For an L-shaped or split-level deck, break the shape into rectangles, calculate each one and add them together. Measure the surface the boards will actually cover, and note anything that interrupts the boards, such as stairs or cut-outs, separately.
Step 2: Work out the cover width
Each board covers its own width plus the ventilation gap beside it. That combined figure is the cover width:
Cover width = board width + gap between boards
Gaps matter for more than arithmetic: they let the deck drain and dry, which protects the timber. Our supplier publishes gap guidance for its products; as one documented example, 140 x 19 mm Peninsula Blonde decking requires a minimum 7 mm gap between boards, which is wider than the 4 mm our calculator assumes by default. Use the gap your product's installation guidelines specify.
Step 3: Convert area to linear metres
Linear metres = deck area in m2 divided by cover width in metres
A worked example: a 20 m2 deck laid with boards at a 90 mm cover width.
- Cover width: 90 mm = 0.090 m
- Linear metres: 20 divided by 0.090 = about 222 lm
- Add 10 percent wastage: about 245 lm
That 245 lm is the quantity to order, not the raw 222.
Step 4: Allow for wastage
Wastage covers cutting to length, docking out defects near board ends, and the offcuts that every deck produces. A 10 percent allowance is a sensible starting point for a straightforward rectangular deck. Consider allowing more when the design works against the board: diagonal laying patterns, picture frames and borders, multiple angles or curves, and lots of small cut-outs all generate more offcut. Running short of hardwood mid-job can mean waiting on supplier availability for more, so the allowance is cheap insurance.
Step 5: Think about lengths
Most of our hardwood decking is supplied in random lengths, with preferred individual lengths available by quote against current supplier availability. As a documented example of the spread, Merbau decking boards run from 1800 to 5700 mm in random lengths. If your deck design needs particular lengths, say so in your quote request: ordering lengths that suit your joist layout and deck dimensions reduces wastage, because butt joints must land on joists.
Step 6: Check it with the calculator
The timber calculator runs this whole conversion for you: enter your deck area, board profile and wastage allowance and it returns linear metres with the working shown. From a product page you can also open the calculator with that board's profile prefilled.
From linear metres to a price
The linear metre rate is shown on every product page, so once you have your quantity you can add your metres to the cart and check out. For pack quantities, preferred lengths or trade volumes, request a quote with the species and profile you want. If you are still choosing a species, the hardwood comparison table and the decking collection are the places to start, and there are more measuring articles on the timber guides blog.
Reviewed by the Sydney Timber Supply team. Last updated 25 August 2026.