Planning your new deck build is an exciting prospect. You’re not just adding a structure to your home; you’re creating a space for family barbecues, quiet morning coffees, and memories that will last a lifetime. But before you can fire up the grill, there’s a crucial planning step that can make or break your project: figuring out exactly how many deck boards you’ll need.
Miscalculating your deck board quantity can lead to frustrating delays, extra delivery charges, and even a mismatched final product if you have to reorder from a different batch. This guide will walk you through the process of calculating your deck board needs, ensuring you get it right the first time.
Step 1: Measure Your Deck’s Square Footage
First things first, you need to know the size of the space you’re working with. Grab a tape measure and, if possible, a helper, and measure the length and width of your planned deck. Multiply these two numbers together to get the total square footage.
- Example: If your deck will be 20 feet long and 12 feet wide, your total area is 240 square feet (20 x 12 = 240).
If you’re planning a more complex, multi-level, or uniquely shaped deck, break it down into smaller rectangular sections. Calculate the square footage of each section and then add them all together for your grand total.
Step 2: Choose Your Deck Boards
Now for the fun part: choosing the right decking material and size of your deck boards. This is a significant decision that will impact the look, feel, and longevity of your deck. Whether you opt for the classic appeal of a material meeting industry standards for pressure-treated wood or the low-maintenance convenience of composite decking, the width of the boards you choose is essential for the next step in our calculation.
Here’s a quick look at common deck board sizes. It’s important to note the “nominal” size (what it’s called at the store) versus the “actual” size (its true dimensions).
| Nominal Size | Actual Width |
| 1×6 | 5.5 inches |
| 2×6 | 5.5 inches |
| 5/4×6 | 5.5 inches |
For most residential decks in the Pennsylvania area, the 5.5-inch actual width is the most popular choice.
Step 3: Don’t Forget the Gap!
Your deck boards won’t be installed flush against each other. A small gap is necessary to allow for drainage and the natural expansion and contraction of the material. The standard gap size is typically 1/8 inch (0.125 inches).
To simplify your calculation, you’ll add this gap to the actual width of your deck board.
- Example: For a 5.5-inch board with a 1/8-inch gap, the total width you’ll use for your calculation is 5.625 inches (5.5 + 0.125 = 5.625).
Step 4: The Magic Formula to Calculate Deck Boards
Now it’s time to put it all together. Here’s the formula to determine the number of boards you’ll need:
(Deck Width in Inches / Total Board Width with Gap) = Number of Boards Needed
Let’s use our 20-foot by 12-foot deck example. The boards will run the length of the deck (the 20-foot side), so we’ll use the width (12 feet) for this calculation.
- Convert the deck width to inches: 12 feet x 12 inches/foot = 144 inches.
- Use the board width with the gap: 5.625 inches.
- Divide: 144 / 5.625 = 25.6
Since you can’t buy 0.6 of a board, you’ll always round up. In this case, you’ll need 26 boards that are 20 feet long.
What About Diagonal Decking?
A diagonal or herringbone pattern can add a touch of elegance to your deck, but it also requires more material. A good rule of thumb is to add an extra 15% to your total board count for a diagonal layout.
Step 5: Always Account for Waste
Even with the most careful planning, there will be some waste from cuts, angles, and the occasional mistake. It’s always better to have a little extra than to run out mid-project. We recommend adding 10-15% to your total board count for waste.
- Example: For our 26-board project, a 10% waste factor would mean ordering an additional 2.6 boards. Since you can’t buy partial boards, you’d round up and order 3 extra, for a total of 29 boards.
FAQs About Calculating Deck Board Quantity
- How many deck boards do I need for a 12×12 deck? A 12×12 deck has a width of 144 inches. Using a standard 5.5-inch board with a 1/8-inch gap (5.625 inches total), you would need 26 boards (144 / 5.625 = 25.6). For a deck this size, exploring small deck designs can help you make the most of your space. Don’t forget to add 10-15% for waste.
- Does the length of the board affect the calculation? The length of the board doesn’t change the number of boards you need to cover the width of your deck, but it’s a crucial factor in minimizing seams and waste. For our 20-foot long deck, using 20-foot boards is the most efficient choice. If you were to use 10-foot boards, you’d need twice as many (52 boards) to cover the same area.
- What if I’m using composite decking? The same calculation method applies to composite decking. The key is to know the actual width of the boards you’re using and the manufacturer’s recommended gap size.
Conclusion: Plan Now, Relax Later
Calculating your deck board quantity might seem like a chore, but it’s a fundamental step in building a safe and beautiful structure. By taking the time to measure accurately, account for spacing, and factor in waste according to deck safety best practices, you’ll be well on your way to building the deck of your dreams.
Of course, the easiest way to ensure a perfect deck is to work with experienced professionals. At Bucksmont Decks, we’ve perfected our professional installation process while designing and building beautiful, high-quality decks for homeowners in the Pennsylvania communities we serve for years. We can handle everything from design and material selection to the final installation, so all you have to do is relax and enjoy your new outdoor living space.
Ready to start your deck project? Request a free estimate today and let’s bring your vision to life!
