How many deck boards do I need for a 12x20 deck?

For a 12×20 deck using 2×6 boards (5.5" wide = 0.458 ft): Number of rows = ⌈12 ÷ 0.458⌉ = 27 rows × 1.10 waste = approximately 30 boards, each 20 ft long.

What is standard joist spacing for a deck?

Standard joist spacing for a residential deck is 16 inches on center (16" O.C.) for most wood and composite decking. Some composite products allow 24" spacing, while others in specific applications require 12" spacing. Always check your decking manufacturer's recommendations.

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🛠️ Construction & DIY

Deck Framing & Material Estimator

Estimate deck boards, joists, posts, and concrete needed for any deck build based on dimensions and spacing.

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Deck Length (ft)

Deck Width (ft)

Board Width (inches)

Joist Spacing (inches)

Include 10% Waste Buffer

Deck Framing & Board Estimation

Deck material estimation requires calculating the number of deck boards (running perpendicular to joists) and the joists themselves. Standard deck boards are 2×6 (actual 5.5" wide) or 2×4 (actual 3.5" wide). Joists are typically spaced 16" on center for structural integrity with composite or wood decking.

Deck Board Count Formula

Rows of Boards = ⌈Deck Width ÷ Board Width (in ft)⌉ × 1.10 (waste)

Joists Needed = ⌊Deck Length ÷ Spacing⌋ + 1

Material Selection

Pressure-treated lumber is the most economical option. Composite decking (Trex, TimberTech) costs more upfront but requires minimal maintenance. Hardwoods (Ipe, Tigerwood) offer premium aesthetics but require sealing. Always check local code for post size and spacing requirements.

Deck Framing & Material Estimator

Deck Boards Required

Deck Framing & Board Estimation

Deck Board Count Formula

Material Selection