Stair Calculator
Steps, risers, stringer.
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Deck Calculator
Enter deck size and board width to get the deck boards and linear feet needed.
Deck boards
—
Boards running the length.
| Deck area | — |
|---|---|
| Linear feet | — |
| With 10% waste | — |
| Board rows | — |
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Enter your figures above to see the step-by-step working.
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How the Deck Calculator Works
Decking boards run across the deck, so the number of boards is the deck’s width divided by each board’s width plus the expansion gap between boards (a common gap is ⅛ inch). Multiply the number of boards by the deck’s length to get the total linear feet of decking to buy, then add about 10% for cuts and waste.
Standard deck boards are 5½ inches wide. Buy boards in lengths that divide evenly into your deck to minimise waste and seams, and remember to plan joists and fasteners separately.
boards = ceil(deck width ÷ (board width + gap))
Frequently Asked Questions
How many deck boards do I need?
Divide the deck width by the board width plus the gap for the number of rows, then multiply by the deck length for total linear feet. Add 10% waste.
What gap should I leave between deck boards?
About ⅛ inch is common for pressure-treated lumber, which shrinks as it dries. Composite boards follow the manufacturer’s spec.
Does this include joists?
No — it covers the decking boards. Joists, beams, posts and fasteners are figured separately based on your framing plan.
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