🏗️ Deck Calculator
Calculate decking materials needed
Recommended: 1/8" (0.125") gap
How to Use This Calculator
Enter Deck Dimensions
Input the length and width of your deck in feet. Measure the deck area where you'll be installing decking boards. For irregular shapes, break into rectangles.
Select Board Width
Choose your decking board width from the dropdown. Common sizes are 2×4 (3.5" actual), 2×6 (5.5" actual), or 2×8 (7.25" actual). Wider boards mean fewer pieces needed.
Set Gap Between Boards
Enter the gap between decking boards in inches. Standard gap is 1/8 inch (0.125") for water drainage. Larger gaps allow more drainage but use more boards. The calculator accounts for gaps automatically.
Calculate and Order
Click "Calculate Decking" to see the number of boards needed and total linear feet. Add 10% extra for waste, cuts, and mistakes. Order all boards from the same batch for color consistency.
Formula
Deck Area = Length × Width
Effective Width = Board Width + Gap
Boards Needed = (Width × 12) ÷ Effective Width
Total Linear Feet = Boards Needed × Length
Example 1: Standard Deck (20 ft × 12 ft, 2×6 boards, 1/8" gap)
Step 1: Calculate deck area: 20 × 12 = 240 sq ft
Step 2: Convert width to inches: 12 ft = 144 inches
Step 3: Effective width: 5.5" + 0.125" = 5.625 inches
Step 4: Calculate boards: 144 ÷ 5.625 = 25.6 → 26 boards
Step 5: Calculate linear feet: 26 × 20 = 520 linear feet
Example 2: Large Deck (30 ft × 16 ft, 2×6 boards, 1/8" gap)
Step 1: Calculate deck area: 30 × 16 = 480 sq ft
Step 2: Convert width: 16 ft = 192 inches
Step 3: Effective width: 5.625 inches (same as above)
Step 4: Calculate boards: 192 ÷ 5.625 = 34.1 → 35 boards
Step 5: Calculate linear feet: 35 × 30 = 1,050 linear feet
About Deck Calculator
The Deck Calculator is an essential tool for homeowners, contractors, carpenters, and DIY enthusiasts who need to accurately determine how many decking boards are required for their deck projects. This calculator eliminates guesswork by providing precise board counts and linear feet calculations, accounting for board width and gaps between boards, helping you order the right amount of materials without waste or shortages.
When to Use This Calculator
- New Deck Construction: Calculate decking boards needed for new deck installations
- Deck Replacement: Determine board quantities for replacing worn or damaged deck boards
- Deck Expansion: Estimate materials for expanding existing decks or adding deck sections
- Budget Planning: Calculate material costs by determining exact board quantities needed
- Contractor Estimates: Quick reference for contractors bidding deck projects
Why Use Our Calculator?
- ✅ Accurate Board Count: Calculates exact number of boards needed accounting for gaps
- ✅ Linear Feet Calculation: Shows total linear feet needed for ordering from suppliers
- ✅ Multiple Board Sizes: Supports different board widths (2×4, 2×6, 2×8) for various deck styles
- ✅ Gap Calculation: Automatically accounts for gaps between boards for proper spacing
- ✅ Cost Planning: Helps budget accurately by determining exact material needs
- ✅ Time Savings: Instant calculations eliminate manual math and measurements
Common Applications
Residential Decks: Homeowners and contractors planning new decks or deck replacements use this calculator to order the correct quantity of decking boards. Standard spacing ensures proper drainage while minimizing board usage, and accurate calculations prevent costly mistakes.
Commercial Decks: Contractors working on commercial deck projects use this tool to estimate materials for larger decks, ensuring sufficient materials are on-site before starting work.
DIY Projects: DIY enthusiasts planning weekend deck projects use this calculator to determine materials needed, avoiding costly mistakes from ordering too little or too much decking.
Tips for Best Results
- Board Widths: 2×6 boards are most common; 2×8 for wider spans; 2×4 for tighter budgets
- Gap Spacing: Standard 1/8" gap allows drainage; larger gaps (1/4") for wet climates
- Add Waste: Always add 10% extra for waste, cuts around posts/railings, and mistakes
- Material Selection: Use pressure-treated lumber for ground contact; cedar or composite for appearance
- Order Together: Order all boards from the same batch/lot for color consistency
Frequently Asked Questions
How many deck boards do I need for a 20×12 foot deck?
For a 20×12 foot deck using 2×6 boards (5.5" wide) with 1/8" gaps, you'll need approximately 26 boards, totaling 520 linear feet. Add 10% extra (3 boards) for waste, so order 29 boards total.
What size deck boards should I use?
2×6 boards are most common for decks—good balance of cost and appearance. 2×8 boards are wider but cost more. 2×4 boards are narrower and cheaper but require more boards. Choose based on budget and appearance preference.
How much gap should I leave between deck boards?
Standard gap is 1/8 inch (0.125") for proper water drainage. In wet climates, use 1/4 inch (0.25") for better drainage. Use decking spacers for consistent gaps during installation.
Do I need to order extra deck boards?
Yes! Always add 10% extra for waste, cuts around posts and railings, and mistakes. Save extra boards for future repairs and replacements. Composite and PVC decking colors can vary between batches.
How do I calculate deck boards for an irregular deck shape?
Divide irregular decks into rectangles, calculate each section separately, then add the board counts together. Or calculate based on total deck area and average board width, then add 15-20% extra for complex shapes.
Should I use pressure-treated or composite decking?
Pressure-treated lumber is cheaper ($1-2 per linear foot) but requires staining and maintenance. Composite/PVC is more expensive ($4-10 per linear foot) but low-maintenance and long-lasting. Choose based on budget and maintenance preference.