Decking Boards Calculator
Calculate how many decking boards you need for your area, including waste and fixing material.
For the surface of a terrace, board length, width and the gap to the next board matter most. For the joist count of the substructure, also check our Deck Substructure Planner. To the substructure planner →
Pro tips
- Even with wood decking, always plan a 3-5 mm gap – boards expand and contract.
- WPC composite boards usually need a slightly wider gap than solid wood.
Frequently Asked Questions
How much waste should I allow for decking boards?
10% is usually enough for simple layouts; for diagonal patterns or lots of corners, allow more like 15-20%.
What gap width is typical for wood decking boards?
Usually 4-6 mm, so the boards can swell with moisture without warping. WPC boards often need a bit more.
How should decking boards be oriented?
Usually laid perpendicular to the main viewing direction from the house – it looks visually calmer and follows the substructure's layout.
How many boards do I need for 20 m²?
It depends on the board format – for 4 m long, 145 mm wide boards with a 5 mm gap, 20 m² with 10% waste works out to about 37 boards. The calculator above works this out for your dimensions.