Decking Calculator
Estimate deck boards from your deck size and board dimensions.
Enter your deck dimensions and your board size and spacing to get the number of deck boards needed, plus the total linear footage. A waste allowance covers cuts and the occasional warped board.
How it works
Each board (plus its gap) covers a strip of the deck. Divide the deck width by the board-plus-gap width to get the number of rows, multiply by the deck length for total linear feet, then divide by board length and add waste. Standard boards are 5.5 inches wide with a 1/8-inch gap.
Frequently asked questions
How many deck boards do I need?
Divide deck width by your board-plus-gap width for the number of rows, multiply by deck length for linear feet, then divide by board length and add waste. A 16×12 deck with 8-ft boards needs about 57 boards.
What gap should I leave between deck boards?
About 1/8 inch for kiln-dried lumber that will shrink, or a small gap for composite. Gaps let water drain and air circulate.
How much waste should I add for decking?
Around 10% covers cuts and the occasional bad board, more if your deck has angles, picture-frame borders, or diagonal patterns.
Is this calculator free and private?
Yes. Every CubicCabin calculator runs entirely in your browser, so the numbers you enter are never uploaded or stored. There's no sign-up, no limits, and it keeps working even if you lose connection after the page loads.