# Decking Calculator Calculate exactly how many deck boards, linear feet, and screws you need for your project. Canonical page: https://invoicemama.com/calculators/decking-calculator This is a free browser calculator. Treat results as planning aids and confirm figures against your own measurements, codes, and professional judgment. ## How to use this decking calculator Enter deck dimensions, board width, spacing, and optional waste to estimate how many deck boards, linear feet of decking, and fasteners you need. ### 1. Measure your deck area Enter the length and width of the deck surface you are covering. For irregular shapes, break the deck into rectangles and run separate estimates, or use an outline area that matches how you will lay boards. ### 2. Set board and gap size Choose the actual width of each deck board (nominal versus dressed size) and the gap you plan between boards for drainage and expansion. ### 3. Add layout details Select a lay pattern if the calculator asks for it (straight, diagonal, etc.) because patterns change cut waste. Increase waste percentage if you expect many angles or curved borders. ### 4. Review materials list Use the board count, linear feet, and screw or fastener estimates to order materials. Confirm joist spacing and fastener schedules against your decking manufacturer guide. ## Frequently asked questions ### How many deck boards do I need for my project? The number of deck boards depends on your deck size, board dimensions, and installation angle. For a standard 12x20 ft deck (3.6m x 6m, or about 22 m²) using 5/4" x 6" boards at 12 feet long, you will need approximately 38-40 boards with 5% waste for 90° installation. Our calculator factors in board width, length, joist spacing, and recommended waste percentage for accurate results. ### What is the most common deck board size? 5/4" x 6" is the most popular deck board size for residential projects. The "5/4" means the board is 1.25 inches thick (actual), while the width is 5.5 inches (actual). This size offers a good balance between durability, cost, and appearance. For heavier traffic areas, 2" x 6" boards provide extra strength. ### How do I calculate square footage or square meters for a deck? Multiply your deck length by its width to get the area. For example, a 20 ft x 12 ft deck equals 240 square feet (or 6m x 3.6m = 22 square meters). For irregular shapes, divide the deck into rectangles, calculate each section, and add them together. Our calculator supports both imperial (feet) and metric (meters) units. ### What board length should I choose for my deck? Choose board lengths that minimize waste and reduce the number of cuts needed. Common lengths are 8, 10, 12, 16, and 20 feet. If your deck is 12 feet wide, using 12-foot boards means fewer cuts. For a 14-foot deck, 16-foot boards will work better then 12-foot boards that would require splicing. ### How much extra material should I order for waste? Plan for 5% extra material for standard rectangular decks with perpendicular (90°) board installation. For diagonal (45-degree) patterns, add 10% waste. Complex designs with curves, multiple angles, or intricate patterns may require 15-20% or more. Its better to have extra boards than to run short mid-project. ### What gap should I leave between deck boards? Standard gap spacing is 3/16" (about 5mm) between deck boards. This allows for water drainage and wood expansion. Composite decking typically uses 1/8" to 1/4" gaps (3-6mm). For pressure-treated wood that is still wet, you can install boards touching since they will shrink as they dry. ### How many screws do I need for decking? Screw count depends on board angle and joist spacing. For a 200 sq ft deck with 12" on-center joists: perpendicular (90°) installation needs about 870 screws, while diagonal (45°) needs about 620 screws. At 16" on-center spacing, reduce these by 25%. Each board typically needs 2 screws at every joist intersection. Use stainless steel or coated deck screws designed for outdoor use. ### Should I install deck boards at 90 degrees or 45 degrees? Perpendicular (90-degree) installation is more common and uses less material with only 5% waste factor. Diagonal (45-degree) patterns create visual interest but require 10% waste factor due to angled cuts. Diagonal installation also needs closer joist spacing (12" vs 16" on center) for proper support and uses fewer screws per linear foot. ### What is the difference between nominal and actual board size? Nominal size is the name (like 2x6), while actual size is the real measurement after milling. A 2x6 board actually measures 1.5" x 5.5". A 5/4x6 deck board is actually 1" x 5.5". Always use actual dimensions when calculating materials to ensure accurate coverage estimates. ### How do I calculate linear feet of decking needed? Linear feet equals the total number of boards multiplied by their length. For example, 40 boards at 12 feet each equals 480 linear feet (146 linear meters). This measurement helps when comparing prices or ordering materials since lumber is often sold by linear foot. ### Can I use this calculator with metric measurements? Yes! Our decking calculator supports both imperial (feet) and metric (meters) units. Simply toggle between ft and m at the top of the calculator. Enter your deck dimensions in meters, and results will show linear meters alongside the board count. Common conversions: 1 foot = 0.3048 meters, 1 square foot = 0.093 square meters. ## Deck Builders: Streamline Your Paperwork Invoice Mama helps deck contractors create professional estimates and invoices in seconds. Turn your material calculations into polished documents that win jobs and get you paid faster. - [Create your first invoice free](https://app.invoicemama.com/sign-up) --- Invoice Mama is invoicing software for contractors, freelancers, and small businesses. It is not a tax, legal, or accounting firm. For current pricing, use the live pricing page. **More:** [Home](https://invoicemama.com/) - [Pricing](https://invoicemama.com/pricing) - [Guides](https://invoicemama.com/guides) - [Tools](https://invoicemama.com/tools) - [Calculators hub](https://invoicemama.com/calculators)