Deck Board Calculator
Enter your deck dimensions and the board you're using. We'll size the order — boards, screws, and the optimal length to minimize cuts.
Advanced options
- Deck area
- 0 sq ft
- Linear feet of decking
- 0
- Rows of boards
- 0
- Deck screws (3" / 75 mm)
- 0
- Estimated cost (boards only)
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How the deck board calculator works
Decking runs perpendicular to the joists. The number of rows = deck width ÷ (board face width + gap). Linear feet = rows × deck length. Convert to board count by dividing by your board length, with a 10% waste factor for cuts. Screws: typically 4 per board face per joist crossing (2 per joist), so deck length × 2 × rows × 4 screws.
Pick the right board length
For a 16 ft long deck, buy 16-footers if you can — single board run, no end-to-end seams. For a 14 ft deck, 12-footers are cheaper than 16-footers but require an end seam mid-run (looks fine if staggered). Mid-deck butt joints should land on a joist — never floating.
Joist spacing
- Pressure-treated 5/4 decking — 16" OC joists fine.
- Cedar / redwood softwood decking — 16" OC fine, 12" for extra firmness.
- Composite (Trex, etc.) — most manufacturers REQUIRE 12" OC for direct-on-joist installs. Read the spec sheet first.
- Diagonal install — drop one joist spacing tier (e.g. 16" OC → 12" OC) because boards span longer.
Common questions
What's the right gap between boards?
⅛" (3 mm) for pressure-treated lumber installed wet (still drying); will close to 1/16" as it dries. ¼" (6 mm) for kiln-dried or composite (no drying shrinkage). Some composite manufacturers require specific gaps — check the spec sheet.
Stainless or galvanized screws?
Outdoors, always coated deck screws — never plain bright. Hot-dipped galvanized or stainless for the longest life. Cedar and pressure-treated wood have tannins that corrode plain screws. Use coated screws rated for ACQ/MCA pressure-treated lumber if you're using PT.
How much does decking cost?
Pressure-treated 5/4×6: $0.80–$2/linear ft. Cedar: $2–$4. Composite: $3–$8. So a 200 sq ft deck (~700 linear ft of board) ranges $560 (PT) to $5,600 (premium composite) for boards alone. See the cost guides for adjacent material pricing.
For deck stairs, see the deck stairs calculator. To stain or seal your finished deck, see the stain calculator.