How much lumber for a 8×12 ft deck?
Answer
20 boards, 10 joists, 6 posts
Deck area: 96 sq ftDecking boards (5.5" wide, 12' long): 20 boardsJoists (16" on center): 10Posts: 6 (2 beams)Screws: 397Linear feet of decking: 238 ftIncludes 10% waste factor
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How We Calculated This
Boards = ceil(rows × boardsPerRow × 1.10), Joists = ceil(width×12 / spacing) + 1
Area = 8 × 12 = 96 sq ft. Boards = 20 (with 10% waste). Joists = ceil(12×12 / 16) + 1 = 10. Posts = 6.
Related Calculations
How much lumber for a 8×10 ft deck?20 boards, 9 joists, 6 postsHow much lumber for a 10×10 ft deck?25 boards, 9 joists, 6 postsHow much lumber for a 10×12 ft deck?25 boards, 10 joists, 6 postsHow much lumber for a 10×14 ft deck?49 boards, 12 joists, 8 postsHow much lumber for a 10×16 ft deck?49 boards, 13 joists, 8 posts
Calculated using verified formulas. Last updated March 2026.