Deck Wood Calculator
Calculate deck boards (5/4x6 and 2x6), joist layout, linear footage, and screw counts for backyard decks and patios.
458 Total Linear Feet (Includes 10% cutting waste)
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What Is a Deck Wood Calculator?
A deck wood calculator estimates the lumber required to build outdoor decking. It computes 5/4×6 (actual 5.5") or 2×6 surface deck boards, floor joists (12" or 16" on-center), rim joists, and hidden deck fasteners or screws.
How to Use This Calculator
- Enter deck length (along the house) and width (projection outward) in feet.
- Choose preferred board length (12, 16, or 20 feet) to minimize butt joints.
- Select joist spacing (16" OC standard, or 12" OC for composite / diagonal decking).
- View total deck board count, linear footage, joists, and screw estimates.
Deck Board Count Equation
\text{Boards} = \left\lceil \frac{\text{Width (in)}}{5.625} \right\rceil \times \frac{\text{Length (ft)}}{\text{Board Length (ft)}} \times 1.10A 5/4×6 board has an actual width of 5.5 inches. Adding a 1/8" gap between boards equals 5.625" coverage per row. A 10% waste buffer is included.
Worked Example
Scenario: Building a 16 ft long by 12 ft wide deck using 16-foot 5/4x6 treated decking boards with 16" OC joists.
Rows of boards: (12 ft × 12) ÷ 5.625 in = 144 ÷ 5.625 = 25.6 -> 26 rows.
Linear feet: 26 rows × 16 ft = 416 LF (+ 10% waste = 458 LF).
Board count: 458 LF ÷ 16 ft = 29 boards.
Floor joists (@ 16" OC): (16 ÷ 1.333) + 1 = 13 joists + 56 LF rim joist.
Screws: 192 sq ft × 3.5 screws/sq ft ≈ 672 deck screws.
Tips & Key Notes
- Install deck boards with the bark side up (growth rings curving downward like a smile) to minimize cupping.
- Composite decking (Trex, TimberTech) requires 12" on-center joist spacing when laid diagonally at a 45-degree angle.
- Apply joist tape (butyl flashing tape) on top of pressure-treated joists before fastening decking to prevent rot at screw penetration points.
Frequently Asked Questions
What is the actual size of a 5/4x6 deck board?
A standard 5/4×6 deck board measures 1.0 inch thick by 5.5 inches wide with rounded radius edges.
How much space should you leave between deck boards?
Leave a 1/8-inch to 3/16-inch gap (the width of an 8d or 10d nail) to allow water drainage and expansion. Wet pressure-treated boards can be installed tight as they will shrink naturally.
How many screws do you need per deck board?
Plan for two screws at every joist crossing. For a 16-foot board over joists spaced 16" on-center (13 crossings), you need 26 screws per board (approx 3.5 screws per square foot of deck).
What is the maximum span for 2x8 deck joists?
At 16 inches on-center with a 40 psf live load, southern pine 2x8 joists can span up to 13 feet without center beam support.
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