Deck Board Calculator

Deck length (ft). Measure one overall side of the rectangular deck surface being covered. Use the finished decking boundaries, not the ledger length if the decking extends beyond it. Picture frames, angled borders and separate deck sections need their own takeoffs.

Deck width (ft). Measure the deck perpendicular to the length. Together these dimensions define the rectangular area covered by parallel board courses. The direction selected below decides which dimension each course runs along.

Actual board width (in). Measure the actual face width of the decking board, or use the manufacturer’s stated installed face width. Do not substitute the nominal lumber name. Wider boards generally require fewer courses across the deck.

Gap between boards (in). Enter the clear space planned between adjacent board edges. Use the spacing required for the selected product and installation conditions. This is an edge-to-edge gap, not an on-center measurement; a blank value means no gap.

Boards run along. Choose whether the boards run along the entered length or width. Each course follows that direction, while the course count is worked out across the perpendicular dimension. A course may require more than one stock board if there are butt joints.

Waste allowance (%). Enter the percentage you want to add for cutting, handling loss or other conditions specific to this work. Apply it to the measured quantity rather than enlarging the measurements as well. The suggested value is editable, not a universal recommendation; enter zero when no allowance is needed.

Courses are the parallel rows needed across the deck, not the number of stock boards to buy. Course length is the distance one row runs, installed linear footage totals all rows, and required footage adds waste. Select stock lengths and plan joints separately. The last course may need to be ripped to width.

Courses = round up((cross-deck width in inches + gap) ÷ (board width + gap)).
Installed linear feet = courses × board run in feet.
Required linear feet = installed linear feet × (1 + waste ÷ 100).

Worked example: A 12 × 10 ft deck with boards along the 12 ft length, 5.5-inch actual board width, and 0.125-inch gaps needs round up(120.125 ÷ 5.625) = 22 courses. Installed length is 264 linear ft; with 10% waste, allow 290.4 linear ft.

Rectangular, parallel courses only. No stock-length optimization, splice planning, or structural joist/beam design. Select board lengths and allow for cuts and end joints separately; the last course may need ripping.