Deck Board Calculator
Calculate how much decking you need from your deck size, board width, spacing, and waste allowance.
Deck board calculator
Measurement system
Deck size
Enter deck length in the direction the boards will run. Deck width is measured across the boards.
Board size
Spacing
Waste allowance
Allow extra for cuts and waste.
BOARD WIDTHGAP
Results
Rows of decking—
Total board length—
Total with waste—
Board length—
Estimated boards required—
Estimated boards incl. waste—
Estimated from full board lengths and the waste allowance.
Enter your deck dimensions to see the estimate.
All boards equal length?
Frequently asked questions
To calculate how many deck boards you need, you need the dimensions of the deck, the width of the boards, and the gap between them. The Deck Board Calculator uses these measurements to estimate the total linear length of decking required. You can also add a waste allowance for cuts, damaged boards, and other material losses. If all of your boards are the same length, you can enter that length to estimate the number of whole boards required.
The correct gap between deck boards depends on the decking material, moisture content, installation conditions, and the manufacturer's recommendations. Because there is no single spacing that is right for every deck, the calculator lets you enter the gap you plan to use.
Extra material is useful for cuts, damaged boards, defects, and mistakes during installation. A waste allowance of around 5–10% is common for straightforward layouts, while more complex designs may require more. Always consider the layout of your deck and the recommendations of your decking supplier.
Yes. The gap between each board contributes to the total width covered by the decking. A larger gap means fewer rows of boards may be required across the same deck width, while a smaller gap may require more. The Deck Board Calculator includes your chosen gap when calculating the result.
Yes. Select Metric or Imperial at the top of the calculator. The selected unit system applies to the entire calculation, so you do not need to choose units separately for each measurement. If you switch between Metric and Imperial, the entered measurements are converted automatically.