Enter your deck dimensions to calculate the exact number of deck boards and linear footage needed. Adjustable for board size, gap, and waste factor.
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Deck Dimensions
Decking Board Size
Gap Between Boards
0.25"Price per Linear Foot
Waste Factor
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Try Suparate FreeAlways install boards crown-side up
Sight down each board before fastening — the slight arch (crown) should face up. This lets water shed off the surface and prevents boards from cupping into water-collecting troughs over time, which is the leading cause of premature deck board rot.
Pre-drill within 3 inches of board ends
Driving screws near the end of a pressure-treated board without a pilot hole almost always causes splitting, especially in drier lumber. A quick pre-drill takes 5 seconds per fastener and keeps your boards crack-free for years.
Acclimate boards on-site before installing
Stack your pressure-treated boards on stickers (small spacers) in a shaded, flat area on-site for at least 48 hours before installation. This lets moisture equalize across all boards and significantly reduces post-install warping and twisting.
A 12×16 deck (192 sq ft) using 5/4×6 boards (actual 5.5" wide) with 1/4" gaps needs approximately 38 boards running the 16-foot length. Adding a standard 10% waste factor brings the total to about 42 boards. The exact count shifts with your chosen board width, gap size, and whether you're running boards parallel or diagonal to the house.
5/4×6 pressure-treated lumber (actual 1" × 5.5") is the most popular choice for residential decks — it balances strength, weight, and cost well. 2×6 boards are a good upgrade for heavier traffic or longer joist spans. For joist spacing over 24 inches on center, use 2×6 or thicker decking to prevent noticeable flex underfoot.
A 1/4-inch gap between boards is the standard for pressure-treated wood — it allows water to drain without letting too much debris fall through. Green (freshly cut) treated lumber will shrink as it dries, so some builders butt boards tight knowing natural gaps will form. For composite and PVC decking, always follow the manufacturer's spacing spec, typically 3/16" to 1/4", since those materials expand more with heat.
Use 10% for straight deck layouts with square cuts and minimal obstacles. Bump up to 15% for 45-degree diagonal patterns and 20% for herringbone or picture-frame borders that generate heavy end-cut waste. Always buy at least one extra board beyond your calculated total so you have a match for mid-project replacements and future touch-ups.
Start with the rim joists: two pieces at the deck length plus two at the width. Add interior joists spaced 16 inches on center — divide the deck width by 1.33 to get the count. For a 12×16 deck that means about 9 interior joists at 11 feet each plus rim boards, posts, and a beam. Don't forget blocking at mid-span for joists over 8 feet and ledger hardware if attaching to the house.