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Deck Materials Guide · Updated August 2026
Short answer: divide your deck's width by the board's actual width plus gap, round up for your row count, then add 10% for waste. A 12×16 deck with standard 5.5-inch boards works out to about 29 boards. Here's the full formula and a real worked example.
You don't need a fancy calculator, just five steps:
Using standard 5.5-inch boards with a 3/16-inch gap, running the 16-foot direction so each board spans the deck with no seams:
| Step | Math | Result |
|---|---|---|
| Effective board width | 5.5″ + 0.1875″ gap | 5.6875″ (0.474 ft) |
| Rows needed | 12 ft ÷ 0.474 ft | 25.3 → 26 rows |
| With 10% waste | 26 × 1.1 | 28.6 → 29 boards |
Waste factor and fastener figures below sourced from Omni Calculator's decking calculator. Board dimensions are standard nominal/actual lumber sizing, not specific to one brand.
| Nominal Size | Actual Width | Common Lengths |
|---|---|---|
| 5/4×6 (wood or composite) | 5.5″ | 8, 10, 12, 16, 20 ft |
| 2×6 | 5.5″ | 8, 10, 12, 16 ft |
Actual width can vary slightly by brand and product line, always check the spec sheet for the specific board you're buying before finalizing an order.
Yes. A picture-frame border, boards running perpendicular around the outer edge, adds extra boards, extra cuts at the corners, and more waste than a simple single-direction layout. A diagonal field pattern does the same thing for a different reason: more angled cuts mean more scrap. Neither is a reason to skip the look you want, just budget the extra material before you order, not after you're short a board mid-install.
Composite decking material runs $12 to $22 per square foot on average, versus $2 to $5 per square foot for pressure-treated wood (HomeAdvisor, 2025). Board count and cost go hand in hand, once you know how many boards you need, that number plugs straight into a real project budget. See our full deck cost guide → for the complete breakdown.
Divide your deck's width by the board's actual width plus gap (in feet) to get your row count, then add 10% for waste. A 12x16 deck using standard 5.5-inch boards needs about 29 boards, see the worked example above for the full math.
Composite decking material runs $12 to $22 per square foot on average (HomeAdvisor, 2025), compared to $2 to $5 per square foot for pressure-treated wood. Composite costs more upfront but needs far less annual maintenance.
Composite decking is typically a blend of wood fibers and recycled plastic, often finished with a protective polymer or PVC cap layer for extra resistance to fading, staining, and moisture.
Yes. A picture-frame border runs perpendicular to the field boards, which adds extra boards, extra cuts, and typically more waste than a simple single-direction layout. Budget for it before you order material, not after.
A common rule of thumb is roughly 350 screws per 100 square feet of decking, or about 3.5 fasteners per square foot, though hidden fastener systems change this math.
Written by Ashleigh & Joey, Evoke Design + Build
Husband-and-wife design-build team serving Hampton Roads since 2017. Ashleigh handles design, Joey runs construction. Licensed & insured contractor. Read more about us →
Tell us your deck size and we'll handle materials, layout, and everything else.
