Decking Calculator
Estimate deck boards based on dimensions, board size, and spacing.
Use decimals when needed. This estimate updates live and is safe to tweak before you buy materials.
Decking Buying Guide
This guide helps you turn your decking calculator result into a cleaner purchase plan. Use it when you want fewer return trips, better waste assumptions, and a more realistic cart.
Step 1: Measure twice
Take two independent measurements and use the larger value when they differ. That single decision prevents most material shortages.
Step 2: Set realistic waste
Simple layouts use lower waste, while angled cuts and pattern matching push waste higher. Do not force one waste value for every room.
Step 3: Buy by package unit
Suppliers sell by boxes, bundles, or rolls. Convert your estimate to purchase units and round up once at checkout.
Cost planning rule of thumb
Build your budget in three bands: material-only, material+consumables, and full project with tool contingency. This keeps expectations realistic before you buy.
Recommended for this job
Commonly paired tools and accessories
These are the practical extras people often forget until the last minute, especially when turning a rough estimate into a real purchase list.
Deck screw packWhy this helps: Common add-on that reduces last-minute store runs once the estimate is final.
Hidden fastener kitWhy this helps: Common add-on that reduces last-minute store runs once the estimate is final.
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Decking Calculator FAQ
What is the recommended thickness for decking boards?
The most common thickness for decking boards is 5/4 inch (actually 1 inch thick). This provides a very stable deck assuming you have a joist spacing of a maximum of 16 inches on center. If you want a more exclusive look and a completely rigid feel, you can use 2-inch nominal boards, which allows for joist spacing up to 24 inches. Using thinner boards requires reducing the joist spacing, which means much more lumber in the substructure. We almost exclusively recommend standard 5/4 boards for most backyard projects.
How large should the gap between decking boards be?
The distance between the boards depends entirely on how moist the wood is when you lay it. If you buy freshly pressure-treated wood that is still wet and heavy, it will shrink as it dries in the sun. In such cases, it is recommended that you lay the boards with a minimal gap, for example by using a carpenter's pencil as a spacer (about 1/8 inch). If you use wood that is already bone dry, you must increase the distance to about 1/4 inch, otherwise the boards risk swelling when it rains and snapping the screws.
Why does the calculator add a 10% waste factor?
When building a deck, you will inevitably need to cut boards to fit the dimensions, connect neatly against the house wall, or round corners and posts. These small pieces (the waste) can rarely be used anywhere else in the project. In addition to this, there are almost always boards in the lumber bundle that have large knots, cracks, or are warped. By automatically adding 10% waste to the material calculation, we guarantee that you do not have to drive back to the lumberyard to buy two missing boards when you are almost done. It saves both time and nerves!
Should I use stainless steel or coated screws?
Which screw you should use depends on where the deck is built. Standard coated decking screws work excellently for most normal environments inland without direct exposure. Stainless steel screws (Grade 305 or 316) are an absolute requirement if you build in coastal environments (near salt water), by a pool, or if you use exotic and hard woods like Ipe or Mahogany. We highly recommend stainless steel for all decks if budget allows, as they will never rust and discolor the wood.
Where can I read more about building a deck?
Check out our in-depth guides in the Knowledge Base: How to Choose the Right Dimensions for Your Deck and The Difference Between Treated and Untreated Wood.