Kalkulo / Construction & Renovation / Decking Boards Calculator

Decking Boards Calculator

Calculate how many decking boards you need, based on your deck's dimensions, board width and standard board length.

Number of boards
41
34 rows of 5 m
Number of rows
34
Deck area
20.0 m²

How to use the decking boards calculator

  1. Enter the deck length — the direction the boards will run along.
  2. Enter the deck width — the direction across the boards.
  3. Enter the board width (including the gap between boards) and the standard length of the product you plan to use.

How the board count is calculated

The calculator first finds how many rows of boards are needed across the deck, then works out the total number of boards based on standard board length:

Number of rows = Deck width ÷ Board width
Number of boards = (Number of rows × Deck length) ÷ Standard board length

The board width should include the gap between boards (usually 4-5 mm), since this affects how many rows are needed.

Note: The calculator assumes boards laid in one direction without joints beyond cut end pieces. If your deck has an unusual shape, or boards need to be joined over joists, add a bit of extra margin.

Frequently asked questions

How much gap should I leave between deck boards?

4-6 mm is common to allow the wood to move with moisture, and to let water and debris drain through. Include this gap in the board width you enter in the calculator.

Should I buy extra boards beyond what the calculator shows?

Yes, it's smart to add 5-10% extra for cutting, mistakes, and any future repair, especially if the deck has an irregular shape.

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