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Deck Board Calculator
Work out deck boards, rows, joists and linear feet from your deck size, board width and gap.
Deck board calculator
Board rows: —
Boards to buy: —
Decking: —
Joists: — totalling —
—
—
How to use the Deck Board Calculator
- Enter the deck length and width and choose feet or metres.
- Set the board width, the gap between boards and the joist spacing.
- Read the board count, linear feet and joist count.
Features
- Rows and boards from board width and gap
- Joist count from joist spacing
- Linear feet of decking and joists
- Ten percent waste allowance included
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Frequently Asked Questions
Common questions about the free online deck board calculator.
Divide the deck width in inches by the board width plus the gap, round up to get the rows,
then divide the length by the stock length.
Leave about 1/8 to 1/4 inch (3 to 6 mm) between boards so water drains away and the boards
can expand without buckling.
Joists are usually spaced 16 inches on centre, and 12 inches for diagonal decking or heavy
loads, with blocking between them.
Every joist spans the deck width, so use joists = deck length in inches / joist spacing + 1,
then multiply by the width.
Yes. Add about 10 percent for cuts, defects and mistakes, and more if the deck has angles,
stairs or a herringbone pattern.
Use two screws at every joist crossing, so a 12 foot board over five joists needs ten screws,
roughly 350 per 100 square feet.
Yes. Enter the composite board width and the gap the maker asks for, which is often narrower
than the gap used with timber.
There is no direct area formula because rows matter. Count rows from the width, then multiply
by the length to get linear feet.
Yes. Enter the deck in metres and the board width in inches, and the tool converts both
before counting rows and boards.
Last updated: October 10, 2026