Deck Board & Framing Calculator - Composite & Wood Decking

Calculate how many deck boards, linear feet of decking, joist spacing, and deck screws you need for pressure-treated wood or Trex composite decks.

⚙️ Configuration & Inputs

Deck Length (Parallel to Boards)

Deck Width (Across the Boards)

Board Nominal Width

Waste & Cut Allowance

📊 Results & Analysis

Deck Boards Needed

29 Boards

580 Linear Feet of Decking

Deck Surface Area	240 sq ft
Number of Board Rows	26 Rows
Linear Feet (No Waste)	520 lin ft
Linear Feet (with 10% Waste)	572 lin ft
Floor Joists Required (16" O.C.)	16 Joists
Deck Screws (Boxes of 350)	3 Boxes (~1,050 screws)

Deck Board Layout & Spacing

Standard deck planks—commonly called 5/4 × 6 boards—actually measure 5.5 inches wide. Leaving a 1/8 to 1/4-inch expansion gap between boards ensures proper rainwater drainage and prevents organic rot.

Number of Rows = Deck Width in inches ÷ (Board Width + Gap)

For composite decking (such as Trex or TimberTech), joist spacing must not exceed 16 inches on-center (12 inches for diagonal 45° patterns) to prevent board sagging under foot traffic.

Frequently Asked Questions

Fasten each board with two screws at every joist intersection. For a deck with joists spaced 16 inches on-center, a 16-foot board intersects 13 joists, requiring 26 screws per board.

Pressure-treated pine typically requires a 10% to 15% waste allowance due to warped boards, knots, and splits. Composite decking typically needs only 5% to 8% waste due to precise factory dimensions.