Deck Board Calculator

About this calculator

This calculator figures out how many deck boards you need to buy by dividing the deck's total surface area (or the coverage width of a single board multiplied across the deck's width) by the effective coverage of one board — accounting for the board's actual width plus any gap left between boards for drainage and expansion — then rounding up and adding a waste allowance (typically 10–15%) to cover cutting losses, mistakes and staggered end joints.

DIY homeowners and professional deck builders use this before ordering lumber or composite decking material to avoid running short mid-project (which risks a mismatched dye-lot on a second order) or over-ordering and wasting money. Getting the board count right also depends on the chosen decking pattern (straight, diagonal or herringbone increases waste), the board length available from the supplier, and the joist spacing the boards need to span.