Decking boards and joists
Deck Board Calculator USA 2026
Boards = deck area ÷ (board coverage width including gap × board length), joists = (deck width ÷ joist spacing) + 1, plus a 10% cut-waste factor.
Reviewed by BuildMate Editorial Team Construction Researchers Updated March 2026 2 min read Fact-checked
Deck Calculator — instant results
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Deck area320 sq ft
Decking boards64
Joists (16" O.C.)13
Deck screws1280
Show calculation steps
- Deck area = 20 × 16 = 320 sq ft
- Board coverage = (5.5 ÷ 12) × 12 = 5.50 sq ft
- Boards = ⌈(320 ÷ 5.50) × 1.10⌉ = 64
- Joists = ⌈(16 × 12) ÷ 16⌉ + 1 = 13
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How the decking boards and joists math works
Boards = deck area ÷ (board coverage width including gap × board length), joists = (deck width ÷ joist spacing) + 1, plus a 10% cut-waste factor.
Boards = Area ÷ (Board Width × Board Length) × 1.10
Frequently asked questions
Joist spacing?
16" O.C. is standard; 12" for diagonal decking.
Estimates based on 2026 RSMeans USA data and national material averages. Always confirm quantities with your supplier or contractor before ordering.