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Decking Calculator

Find how many decking boards.

Result

32
85.71 m

How it is calculated

The tool works out how many boards cover the deck. Area is in square metres, board width in centimetres and board length in metres. First, the total board length needed: linear metres = area / (width / 100), treating the boards as laid edge to edge. Then boards = ceil(linear metres / board length × 1.1). The 1.1 adds 10% for waste and cuts, and ceil rounds up to a whole board. Width and length must be above zero. The estimate ignores gaps between boards, so spacing for drainage or expansion changes the count slightly, and it does not cover joists or screws.

Worked example

A deck of 12 m² with boards 14 cm wide and 3 m long. Width in metres: 0.14. Linear metres = 12 / 0.14 = 85.71 m. Boards without waste = 85.71 / 3 = 28.57. Add 10%: 28.57 × 1.1 = 31.43. Round up to the next whole board: 32 boards. You would buy 32 boards of 3 m, and the waste allowance covers cut-offs at the edges.

Try this example →

Common mistakes

  • Entering board width in millimetres or metres. The field expects centimetres, so 14 not 140 or 0.14.
  • Entering board length in centimetres. Length is in metres.
  • Leaving out gaps and diagonal layouts: a diagonal pattern wastes more than 10%, so add extra.
  • Measuring the area from the house wall instead of the actual deck surface, or forgetting steps and edges.

About this calculator

This calculator works out how many decking boards and how many linear meters of timber a given deck area needs, based on the board width and the gap left between boards for drainage and expansion.

DIYers and contractors use it when planning a garden deck or patio, to order the right quantity of boards up front rather than under-buying and having to match batches later, or over-buying and wasting material.

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