Deck Board Calculator
Enter your deck dimensions and board size to calculate the number of deck boards, total linear feet of lumber, and square footage needed for your project.
Standard: 1/8" (0.125") gap
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Boards needed
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Linear feet
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Deck area (ft²)
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Rows of boards
How to Calculate Deck Boards
The number of board rows equals the deck width divided by the sum of the board width plus the gap, both in inches. The number of boards per row equals the deck length divided by the board length (rounded up). Multiply rows by boards per row, then add the waste factor.
Board Spacing Guide
| Gap | Notes |
|---|---|
| 1/8" (3 mm) | Allows for expansion; most common |
| 3/16" (5 mm) | Better drainage; good for humid climates |
| 1/4" (6 mm) | Maximum typical spacing; debris can fall through |
| No gap (0") | Only for pre-kiln-dried or composite boards installed tight |
Green or wet lumber will shrink as it dries — gaps close over time. Dry or kiln-dried lumber should be spaced at the final desired gap from day one.
Decking Material Guide
| Species / type | Durability | Maintenance | Notes |
|---|---|---|---|
| Pressure-treated pine | Good | Medium | Most affordable; needs staining/sealing |
| Cedar | Good | Medium | Naturally rot-resistant; pleasant appearance |
| Redwood | Very good | Medium | Premium look; expensive |
| Ipe (Brazilian hardwood) | Excellent | Low | Very dense; very heavy; 25–40 year lifespan |
| Composite decking | Very good | Very low | Expensive upfront; no staining or splinters |
| PVC decking | Excellent | Very low | Fully waterproof; most expensive |
Hidden vs. Surface Fasteners
| Fastener type | Pros | Cons |
|---|---|---|
| Surface screws | Easy to install, low cost | Visible fastener heads |
| Hidden fasteners (grooved boards) | Clean look, no visible screws | Requires grooved boards; higher cost |
| Clip systems | Fast installation | Specific to board brand/profile |
Allow for extra boards in your order if using hidden fasteners — the clips reduce effective coverage slightly. Most hidden fastener systems account for this in their packaging.
Frequently Asked Questions
What is the actual width of a 2×6 deck board?
Lumber is sold by nominal dimension but the actual size is smaller due to milling. A nominal 2×6 measures 1.5 inches thick by 5.5 inches wide. A 5/4×6 deck board (the most common decking profile) is 1 inch thick by 5.375 inches wide. This calculator uses actual widths automatically.
How many deck boards do I need for a 12×16 deck?
A 12×16 ft deck using 5/4×6 boards (5.375" wide) with 1/8" gap and 12-ft boards: approximately 26 rows × 2 boards per row = 52 boards, plus 10% waste = 58 boards. Use this calculator for your exact dimensions.
Should I lay deck boards lengthwise or widthwise?
Boards are typically run perpendicular to the joists (which run the short direction of the deck). The "length" direction of the boards should span the longest dimension of the deck to minimise end cuts. A diagonal pattern requires 15% more material.
