How much decking is used per m²?

It depends on the board width and the gap. With a 95 mm board and a 4 mm gap, each board covers about 99 mm, giving a little over 10 linear metres per m².

How big a gap should I have?

Often 3–6 mm depending on the timber’s moisture content – wood swells and shrinks. Lay dry timber tighter and fresh timber wider.

Does the calculator include the joists and bearers?

Yes, you get linear metres of joists/bearers at your chosen c/c – 600 mm by default. Building tighter? Lower the c/c and the length updates.

Does it cost anything?

No, the calculator is free and requires no account.

Free calculator

Decking calculator

Planning a new deck? The decking calculator turns your area into linear metres and board counts in seconds – the right numbers before you order the timber. Gap and waste are built in, so you won’t come up a board short on delivery day.

Decking calculator – boards and joists

Enter the deck area, board width and gap and we work out the linear metres of decking, the number of boards and the joists/bearers under the deck – incl. waste.

Area (m²)Board width (mm)Gap (mm)Board length (m)Joist c/c (mm)Waste (%)

Linear metres of decking0 lm

Number of boards0 pcs

Joists/bearers (c/c 600)0 lm

An estimate. The gap affects consumption. Joists are counted as total length at the chosen c/c – add posts/piers and fixings separately.

Create quote from this Create invoice

This tool gives an estimate and is an aid – not a finished calculation. Always check the result against drawings, applicable regulations, supplier data and your professional experience before giving a binding price, ordering material or using the file. ByggExp is not responsible for decisions made solely on the basis of the tool.

Preview of the decking calculator — This is how the decking calculator looks

How to work out the decking

Work out the deck area in m².
Enter the board width and the gap.
Enter the board length and waste.
See the linear metres and number of boards.

Don’t forget the substructure

The substructure decides how long the deck lasts. Beyond the boards and joists you’ll still need piers or a foundation and fixings. Buy a board or two extra for cuts and future replacements.

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Frequently asked questions

How much decking is used per m²?: It depends on the board width and the gap. With a 95 mm board and a 4 mm gap, each board covers about 99 mm, giving a little over 10 linear metres per m².
How big a gap should I have?: Often 3–6 mm depending on the timber’s moisture content – wood swells and shrinks. Lay dry timber tighter and fresh timber wider.
Does the calculator include the joists and bearers?: Yes, you get linear metres of joists/bearers at your chosen c/c – 600 mm by default. Building tighter? Lower the c/c and the length updates.
Does it cost anything?: No, the calculator is free and requires no account.