Deck Board Calculator
The Deck Board Calculator estimates the number of deck boards needed based on your deck size, board dimensions, and the gap between boards for drainage.
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How This Tool Works
Enter your deck's length and width, your board's length and width, and the gap you plan to leave between boards for drainage.
Formula & Method
Rows across the deck width = (deck width in inches) ÷ (board width + gap). Boards per row = deck length ÷ board length. Total boards include your chosen waste factor.
Example Calculation
A 16×12 ft deck using 12 ft boards that are 5.5 in wide with a 1/8 in gap needs about 32 boards, including a 10% waste allowance.
Frequently Asked Questions
How much gap should I leave between deck boards?+
Most pros leave 1/8 to 3/16 inch between boards for drainage and to allow for natural wood expansion.
Does this account for board direction?+
This calculator assumes boards run the length of the deck. If your boards run the width instead, swap your length and width entries.
Should I buy extra deck boards?+
Yes, the built-in waste factor covers most cutting losses, but keeping a couple of spare boards helps with future repairs or replacing damaged boards.
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