Deck Board & Screw Calculator (Spacing, Waste & Materials)

How to use this calculator

Choose Imperial or Metric and the interface updates so every label and helper line matches your unit system. Enter deck length × width as a simple rectangle. If your deck is L-shaped or notched, split it into rectangles, run each area, then add the totals.

• Board width (actual): many 5/4×6 and 2×6 boards measure 5.5 in (≈140 mm).
• Board gap: usually 1/8–1/4 in (3–6 mm), per manufacturer guidance and climate.
• Stock length: pick sizes commonly available locally; longer boards reduce splices but can increase cost and handling.

Options at a glance

• Pattern: Straight, Diagonal 45°, or Herringbone. Decorative patterns add a modest area multiplier for off-cuts.
• Joist spacing (OC): affects fastener counts (crossings), not board count.
• Fasteners: Screws (2 per joist crossing) or hidden clips (1 per crossing).
• Waste (%): covers kerfs, defects, and handling—use 5–10% for straight runs and 10–15% for diagonal/herringbone.

What your estimate includes

The results show board rows, total lineal length, an approximate piece count at your stock length, joists along the span, and fasteners required per your selection. Counts are rounded up so you don’t run short. End splices add fasteners for blocking rows. Picture framing, borders, stairs, and fascia are not itemized—add those separately to suit your design.

Tips for accurate inputs

Measure with the same tolerance across the deck, confirm the true board width you’ll purchase, and choose a gap that fits your climate and product guidance. For composites, follow manufacturer spacing and approved fasteners. For timber, wetter stock tends to shrink; dry stock can swell with weather. Round your order to practical bundles and keep a small buffer for off-cuts and on-site variation.

Can I switch units later?

Yes. Switching between Imperial and Metric rewrites labels and options. The gap value also converts automatically.

Does joist spacing change board count?

No. Board count depends on deck width, board width, and gap. Joist spacing affects fasteners by changing crossings.

How much waste should I allow?

For straight layouts, 5–10% usually covers off-cuts and defects. Diagonal and herringbone layouts often need 10–15%.

Are stairs, borders, and fascia included?

Not in the core estimate. Add picture frames, fascia, risers, and stair treads separately based on your design.