Deck Builders
Deck Board Calculator
Calculate how many deck boards you need based on deck size, board width, and spacing.
Boards run lengthwise (16′) across the 12′ deck width. 26 rows of boards with 5.5″ width and 0.25″ gaps, plus 10% waste = 29 boards total.
How to figure out how many deck boards you need
The basic math is straightforward. Divide your deck width by the width of each board plus the gap between boards. That gives you the number of rows. Multiply by the deck length to get total linear feet. Then add waste. This calculator handles all of that including waste factor so you can order with confidence.
What size deck boards should I use?
Most residential decks use 5/4x6 boards, which are actually 5.5 inches wide and about 1 inch thick. They are the standard for a reason. They are strong enough to span 16 inch joist spacing, comfortable to walk on, and available everywhere. If you want a beefier look, 2x6 boards work too but cost more and are heavier. For composite decking, check the manufacturer specs because widths vary.
How much gap between deck boards?
Standard gap is 1/4 inch for pressure treated lumber. That allows for drainage and lets the wood expand and contract with the weather. For composite decking, follow the manufacturer's recommendations because it varies. Some composites need 3/16 inch, others need 1/4 inch. If you are building in dry conditions, you might go a little tighter since the wood will expand when it absorbs moisture.
How much extra decking should I buy for waste?
For a standard rectangular deck with boards running straight, buy 10 percent extra. If you are running boards at a 45 degree angle, bump that up to 15 percent because the cuts at the edges waste more material. For a deck with a lot of curves or angles, 15 to 20 percent is safer. Leftover material can always be returned or used for stair treads.
Common Questions
How long do deck boards last?
Pressure treated boards last 15 to 20 years with regular staining. Composite boards can go 25 to 30 years with almost no maintenance.
Composite vs pressure treated decking cost?
Composite runs about $4 to $8 per linear foot. Pressure treated is $1.50 to $3. Composite costs more up front but you save on staining and replacing boards over time.
Can I use 2x6 for decking?
Yes, 2x6 boards work for decking but they are heavier and more likely to cup or warp than standard 5/4x6 deck boards. They are overkill for most residential decks.
What direction should deck boards run?
Run boards perpendicular to the house for the best look and drainage. Running them at a 45 degree angle looks sharp but wastes 15 percent more material on cuts.
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