Deck Board Calculator
Enter your deck dimensions and get the number of decking boards, joists and fasteners. WoodCalc calculates from the actual milled width of 1×6 (5.5 inches), not the 6 inch nominal name — the difference is 8 percent, and getting it wrong means a second trip to the lumber yard.
Usually 1/8–1/4 inch
16 or 24
Results
Enter your measurements above and press Calculate.
Buy the materials this project needs
WoodCalc gives you the shopping list. Pick the items below to source decking boards, framing lumber, fasteners, and finishes at current prices.
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Questions people ask
How many deck boards do I need for a 16×20 deck?
With 1×6 decking at 5.5 inch actual coverage and a 1/4 inch gap, a 16×20 foot deck needs about 138 boards including 10 percent waste. Run the calculator with your own dimensions for the exact count.
Should I use 5/4 or 2×6 decking?
5/4 (1.25 inch) is standard for most residential decks and spans wider. 2×6 is used on taller or longer spans. Both cover the same width — a 2×6 and a 5/4 are both 5.5 inches wide — so the board count is identical; only the thickness and price change.
What joist spacing do I need for a deck?
16 inches on center for most residential decks; you can go to 24 inches on center only if your decking thickness and span allow it. Check the joist span table before assuming 24 OC will save money.
Is decking sold in 8 foot or 12 foot lengths?
Both, and 12 foot boards reduce the number of joints but are harder to transport and often priced higher per foot. This calculator uses 6 foot boards for the per-row count and reports total linear feet so you can compare against 8 foot pricing.
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