Deck Board Calculator for Decking

Divide the deck area by the area one board covers, then add waste and round up. A board covers its face width plus the gap, converted to feet, times its length. For a 192 square foot deck with boards covering about 7.6667 square feet each, that works out to 28 boards after a 10 percent allowance.

Use the actual face width, not the nominal name. A nominal 5/4x6 or 2x6 deck board measures about 5.5 inches wide, which is the default here. Narrow 1x4 decking is closer to 3.5 inches, and some composite planks run 5.375 inches, so check the product spec before you commit.

Boards are spaced so the deck sheds water and the wood can expand and contract. The calculator adds that gap to each board's effective width, so a wider gap makes every row reach a little further and lowers the total slightly. A quarter inch is a common starting point for kiln dried lumber.

Around 10 percent suits a plain rectangular deck laid straight. Diagonal layouts, picture frame borders, breaker boards and many short runs create more offcuts, so raise the figure to 15 or 20 percent for those patterns. It is cheaper to return a couple of boards than to make a second trip mid build.

No. This tool estimates only the surface decking boards. Framing such as joists and beams, plus screws or hidden clips, is sized from your deck plan and local code. Our deck calculator adds joists and screws if you need the full material list.

Yes. A longer board covers more area, so fewer are needed to fill the same deck, though you may cut and waste more at the ends. The count assumes each board is used across its full length, so match the board length to your run direction and joist layout for the most accurate estimate.

Deck length and width are in feet, board width and gap are in inches, and board length is in feet. The result reports deck area and per board coverage in square feet. There is no metric mode, so convert meters to feet first if your plans use metric dimensions.

You cannot buy a fraction of a board, so any leftover area pushes the count to the next whole board. The rounding is guarded against tiny floating point drift, so a value that is mathematically exact is not bumped up by a rounding artifact.

Yes. The whole calculation runs in your browser with no account and no upload, so your dimensions never leave your device. You can use it offline once the page has loaded.