How many deck boards do I need?

You're about to order deck boards and don't want to overspend or come up short. Here's the rule of thumb and a fast way to get the exact number.

Quick answer

For a standard 14 cm wide deck board with a 4–5 mm gap, you'll need about 7 linear metres of board per m² of deck. Add 5–10 % for waste.

How that works out

A 14 cm wide board covers roughly 14.5 cm once you include the gap. Per m² of deck that's 1 ÷ 0.145 = about 7 linear metres.

If you buy 4 m boards, one board covers roughly 0.58 m² – but only if it doesn't need any cutting.

Waste comes from end cuts at edges, joins and corners. For a simple rectangular deck, 5–10 % is plenty. For patterned layouts or angled corners, plan around 15 %.

Example: a 4 × 5 m deck

A 4 × 5 m area is 20 m². At 7 linear metres per m² that's 140 linear metres of board. If you buy 4 m boards, that's 35 boards – plus 10 % waste = 39 boards. Add 1–2 extra if you've got lots of cuts.

Common mistakes

  • Buying exactly the calculated number and skipping waste – you'll always be short two boards on a Sunday afternoon.
  • Using the board's nominal width (e.g. 14 cm) without including the gap – the count comes out too low.
  • Not checking that every board comes from the same batch – colour can shift between batches.
  • Mis-measuring the deck area when there's an inset planter or angled railing.

Get the exact number

Enter your own dimensions, pick a board type and see the exact board, screw and joist count.

Frequently asked questions

What about narrower 12 cm boards?

Roughly 8 linear metres per m². Narrower boards mean more pieces – and a few more screws.

Do I need a lot more for a diagonal layout?

Yes, plan for 15 % waste on a 45° pattern. You end up with a lot of corner cuts.

Does the count include screws and joists?

Boards are calculated by area. Plan around 25–30 screws per m². Joists depend on spacing – usually 40–60 cm centres.

Should I buy spares for future repairs?

It's a smart move. Matching a discontinued batch and shade in a couple of years is almost impossible.

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