Deck Board Calculator
Decking boards and joists for a deck.
| Rows of boards | 26(across 12 ft at 5.75 in per row) |
| Boards needed | 28.6(including 10% waste) |
| Boards to buy | 29 pieces of 16 ft |
| Total board length | 458 lin ft |
| Joists at 16 in centres | 13(running the other way) |
| Board feet (1 in thick) | 210 bd ft |
Results update instantly and are computed entirely in your browser. For general information and planning only — not engineering, structural or code advice.
About the deck board calculator
A deck estimate is really two estimates: the decking surface, which runs one way, and the structure beneath, which runs across it. Getting the first right means thinking in rows of boards rather than in area, because boards are fixed in width and the gap between them is part of the design, not wasted space. The number of rows is the deck width converted to inches, divided by the width of one board plus one gap, rounded up. That gives how many boards you need to span the width, each cut to the length of the deck. Multiplying rows by length gives the linear feet of decking, and dividing by the length of the boards you plan to buy gives the piece count. Wider boards mean fewer joints and faster laying but more visible movement with moisture; narrower boards look busier and are less prone to cupping. The gap is a design choice with consequences. A quarter-inch gap lets water drain and debris pass and allows the boards to swell without buckling. Too narrow and the deck traps water and clogs; too wide and it becomes uncomfortable underfoot and lets small objects through. The gap also reduces the surface area you cover per board, which is why it must be added to the board width when counting rows rather than ignored. This calculator returns rows, boards, total linear feet and the number of joists at your chosen spacing, with a waste allowance for end cuts and defects. It assumes a rectangular deck framed with joists running across the shorter dimension, and does not include posts, beams, stairs or railings, which are estimated separately. Check the span tables for your lumber species before fixing joist spacing.
This calculator returns estimates for planning and general information only. It is not engineering, architectural, structural, electrical or code advice, and it cannot replace a qualified professional who has seen the site. Material quantities depend on the actual dimensions, the product you buy and local building codes, so confirm the figures before ordering materials or starting work, and always follow local regulations.