How do I calculate deck boards needed?

Divide the deck width by the board width plus gap (e.g., 5.5" + 0.25" = 5.75"), round up to the number of rows, then multiply by deck length for total linear feet of decking.

What is the standard gap between deck boards?

The standard gap between deck boards is 1/4 inch (6mm) to allow for drainage and wood expansion. Pressure-treated lumber will shrink as it dries, so new boards can be installed touching.

How much decking do I need per square foot?

For 5/4×6 deck boards (5.5" actual width) with 1/4" gaps, you need about 2.2 linear feet of board per square foot of deck area, including 10% waste.

Should I use 5/4×6 or 2×6 deck boards?

5/4×6 (1" thick) deck boards are lighter and easier to handle. 2×6 boards are stronger and span wider joist spacing. Both are common for residential decks.

How do I add waste to my deck board calculation?

Add 15% waste for a straight layout and 20-25% for diagonal or chevron patterns where more cuts create more waste.

Deck Calculator – DIY Calculators — Free Home Improvement Tools

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Quick Answer

To calculate deck boards needed, divide the deck width by the board width plus gap (e.g., 5.75" for a 5.5" board with 1/4" gap), round up for total rows, then multiply rows by deck length for linear feet. Add 15% for waste from end cuts.

Calculate deck boards, joists, and fasteners for your deck project.

Deck Length (feet) Deck Width (feet) Decking Board Width Board Gap (inches) Joist Spacing

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Cite This Tool

Deck Calculator. (2026). DIY Calculators Online. Retrieved from https://diycalculator.net/deck-calculator/

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