Decking Board Calculator

Reviewed by the CalculatorHub team, edited by James Graham. Method from CalculatorHub methodology. Last verified 2026-06-23.

The Decking Board Calculator computes decking board from the relation rows = ceil( (deck width x 12) / (board width + gap) ); boards = ceil( (rows x deck length / board length) x (1 + waste percent / 100) ). It takes 6 inputs (deck length in ft, deck width in ft, board face width in in, gap between boards in in, board length in ft, waste allowance in %) and returns the decking board. These calculators are for homeowners, renovators, builders, landscapers and tradespeople planning work on a house, yard or site, covering how much material an area will take, how a layout, slope or frame should be set out, and what size or capacity a room, tank or system needs before anything is bought or built. Enter your values below and the result updates instantly, and you can share a permalink that pre-fills the exact calculation. Measure the real space rather than working from nominal figures on a plan, and keep every length, area and volume in one unit system before entering it so feet and metres never get mixed. Where the result is material to buy, treat it as a starting figure and round up, because bags, sheets, rolls and panels come in fixed sizes and some of every order goes to offcuts, breakage and second coats; where the result is a dose, load or size rating, use it as calculated rather than padding it. For example, with deck length = 16 ft, deck width = 10 ft, board face width = 5.5 in, gap between boards = 0.125 in, board length = 12 ft, waste allowance = 10 %, the decking board works out to 33, and the worked example further down the page shows every step so you can follow the arithmetic and reproduce it by hand. The method is the standard form documented by CalculatorHub methodology, and the figure above each result carries the date it was last verified. These are planning figures, not a structural, electrical or safety check. What a job actually consumes shifts with substrate porosity, compaction, ground conditions, waste and each product's own coverage or dose rating, so confirm the final quantity against the product details or with your supplier before ordering, and have any load-bearing, electrical, gas or drainage work designed and checked by a qualified professional.