Deck Materials Calculator

Enter deck dimensions, board size, gap, and joist spacing to get board count, joist count, and fastener count. Materials only — no structural analysis.

Units

Deck Dimensions

Deck Length (ft or m)

Deck Width (ft or m)

Boards & Joists

Board Width (in or cm)2×6 = 5.5", 5/4×6 = 5.5", Trex = 5.5"

Board Gap (in or mm)3/16" = 0.1875" typical

Joist Spacing (in on center)

Fastener Type

Waste Factor (%)

Materials Needed

Board and joist math

Boards run perpendicular to joists. The number of boards is the deck width (perpendicular to board direction) divided by (board width + gap). Joist count depends on spacing: 16" on center means one joist every 16 inches along the deck length, plus one extra at the far end. This calculator assumes standard framing without special conditions (cantilevers, angled sections, framed openings).

Fasteners

Screws: 2 per board per joist. A typical 12×16 deck uses 400–600 deck screws — buy a 5 lb bucket. Hidden fasteners (Camo, Tiger Claw, etc.) use 1 clip per board per joist, plus starter clips at the perimeter. Hidden systems cost more but leave a clean board face.

What this calculator does not compute

Beam sizing, joist span, ledger board attachment, footings and posts, stair stringers, railing components, or code compliance. These are structural questions that depend on your load, span, species, exposure, and local code — hire a licensed deck builder or an engineer if you're building anything above ground level. The materials count here is for planning and pricing, not for engineering the frame.