Decking Material Calculator
Calculate the number of deck boards required for a timber or composite deck, accounting for board dimensions, the gap between boards, and a waste allowance.
Results
What is it?
A decking material calculator works out how many individual boards you need to cover a given deck area. It factors in the gap between boards (important for drainage and wood expansion) and a waste percentage to cover end cuts, defective timber, and diagonal layouts.
How to use
Enter your deck dimensions and the nominal width of each board. Add the intended gap (5 mm is standard) and your board length. The calculator divides the deck width by the effective board pitch (board width + gap) to find rows, then divides deck length by board length to find runs, multiplying for total board count.
Example scenario
A 6 m x 4 m deck (24 m2) using 140 mm boards with a 5 mm gap needs 27.4 boards across the width. With 4.8 m boards, 2 lengths cover the 6 m run. That is 28 x 2 = 56 base boards, plus 10% waste = 62 boards to order.
Pro tip
For diagonal decking layouts, increase waste to 15�20% � cutting boards at 45 degrees produces significantly more off-cuts. Composite decking is typically sold by linear metre, so multiply board count by board length to get the linear metres to order.