Deck Lumber Calculator
Building a deck requires careful material planning. This calculator estimates the complete lumber package: decking boards (with 10% waste), joists, beams, and 4×4 posts based on your deck dimensions. Includes a cost estimate for materials. Check with a structural engineer for spans exceeding manufacturer recommendations.
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Top Pick5/4×6 Cedar Deck Board — Home Depot~$10.98/board* Affiliate links — we may earn a commission at no cost to you.
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How to Use This Calculator
- 1Enter your measurements in the fields above. Use the units shown next to each field (ft, in, etc.).
- 2Click Calculate to get your material estimate instantly.
- 3Review the highlighted result — it shows the key quantity you need to order.
- 4Use Copy Results to save your estimate, or bookmark the URL — your inputs are encoded in the link.
Pro tip: Always add 10% to your material order to account for waste, cuts, and defects.
Frequently Asked Questions
How many decking boards do I need for a 16×12 deck?
A 16×12 ft deck is 192 sq ft. Using 5/4×6 boards (5.5" wide = 0.458 ft), you need 192 ÷ 0.458 ≈ 419 linear feet of decking, or about 26 boards at 16 ft each — plus 10% waste adds 3 more boards, totaling 29 boards.
What size joists do I need for a deck?
For 16-inch OC spacing, 2×8 joists can span up to 14 feet; 2×10 can span up to 17 feet. At 12-inch OC, 2×8 spans up to 16 feet. Always verify with the AWC Span Table or your local building department.