Deck Board Calculator
Calculate how many deck boards you need with optimized layouts to minimize waste. Includes screws and cost estimates.
How to Use This Calculator
Getting the right number of deck boards prevents costly mid-project trips to the lumber yard. Here's how to calculate accurately:
- Enter your deck dimensions. Length is the direction boards will run; width is across the boards.
- Select your board width (5.5" is standard for 2×6 decking after milling).
- Choose the board length that best fits your deck width to minimize waste and seams.
- Adjust the waste factor based on your pattern (10% straight, 15-20% diagonal).
- Click 'Calculate' to see boards needed and compare different board lengths.
Why This Matters
Deck boards are a significant expense, and improper planning leads to wasted material or frustrating trips back to the store. Choosing the optimal board length for your deck width can save 10-20% on materials. Understanding where seams fall helps plan a professional-looking installation.
- Calculate exact board counts with waste factor
- Compare different board lengths to minimize waste
- Know how many screws and fasteners you need
- Estimate total project cost accurately
- Plan seam locations before you start
Worked Examples
Standard Rectangular Deck
A 12' × 16' deck using 5.5" wide boards running the 16' length.
Calculation: 12' ÷ (5.625" / 12) = 26 rows. Each row needs one 16' board. 26 boards + 10% waste = 29 boards.
Result: Order 29 boards (16' lengths). Full-span boards mean no seams.
Wide Deck with Seams
A 20' × 24' deck using 12' boards.
Calculation: 20' ÷ (5.625" / 12) = 43 rows. Each row needs 2 boards (12' each). 86 boards + 10% waste = 95 boards.
Result: Order 95 boards. Plan seams to stagger and fall on joists.
Diagonal Pattern
A 14' × 14' deck with 45-degree diagonal boards.
Calculation: 196 sq ft deck. Standard would need ~42 boards. Diagonal adds 15% waste = 49 boards.
Result: Order 50+ boards. Diagonal cuts waste more material at edges.
Common Mistakes to Avoid
- Not accounting for the actual board width - a '2×6' is only 5.5" wide after milling.
- Forgetting the gap between boards - gaps reduce coverage per row.
- Using board lengths that create excessive waste - match board length to deck width when possible.
- Not planning seam locations - seams must fall on joist centers.
- Underestimating waste for diagonal patterns - diagonals waste 15-20% more than straight layouts.