Deck Builder Calculator – Loan calculator

Deck Material Estimator

Planning to build a deck? Our Deck Material Estimator helps you get a quick estimate of the main lumber components you'll need. Simply enter your desired deck dimensions and common material specifications, and the calculator will provide an approximation of decking boards, joists, beams, and support posts. This tool is designed to give you a starting point for your material list, helping you budget and plan your project more effectively.

Deck Length (feet):

Deck Width (feet):

Deck Height (feet, from ground):

Joist Spacing (inches, on center): 12 inches 16 inches 24 inches

Decking Board Width (inches, actual): 3.5 inches (e.g., 1×4 or 5/4×4) 5.5 inches (e.g., 1×6 or 5/4×6)

Max Beam Span (feet):

Estimated Materials

Total Deck Area: sq ft

Linear Feet of Decking: linear feet (includes 10% waste)

Estimated 12ft Decking Boards: boards

Number of Joists: (running across deck width)

Number of Beams: (running along deck length)

Number of Support Posts:

Estimated Post Length: feet (includes 1ft for embedment/cutting)

Note: This is an estimate. Always consult local building codes and a professional for precise material lists and structural requirements.

Understanding Your Deck Material Estimate

Building a deck involves several key components, and understanding how they are calculated can help you visualize your project.

Inputs Explained:

Deck Length (feet): The longer dimension of your rectangular deck.
Deck Width (feet): The shorter dimension of your rectangular deck.
Deck Height (feet, from ground): The desired height of your deck surface from the ground. This helps estimate post lengths.
Joist Spacing (inches, on center): The distance from the center of one joist to the center of the next. Common spacings are 12″, 16″, or 24″. Wider spacing requires stronger joists and decking.
Decking Board Width (inches, actual): The actual width of the decking boards you plan to use (e.g., a nominal 6-inch board is often 5.5 inches actual width).
Max Beam Span (feet): The maximum distance your chosen beam material can span without needing a support post. This is crucial for determining the number of posts.

Outputs Explained:

Total Deck Area (sq ft): The total surface area of your deck, useful for estimating finishes like stain or paint.
Linear Feet of Decking: The total length of decking boards required to cover the entire deck surface, including a 10% waste factor for cuts and mistakes.
Estimated 12ft Decking Boards: An approximation of how many individual 12-foot decking boards you would need based on the total linear feet. Adjust this based on available board lengths (e.g., 16ft, 20ft).
Number of Joists: The horizontal framing members that support the decking. This calculation assumes joists run perpendicular to the deck's length, spanning its width.
Number of Beams: The main structural members that support the joists. For a simple rectangular deck, two beams running the length of the deck are typically assumed.
Number of Support Posts: Vertical members that support the beams. The quantity depends on the deck length and your chosen maximum beam span.
Estimated Post Length: The approximate length of each support post, including an extra foot for embedding in concrete footings or for cutting to final height.

Example Calculation:

Let's say you want to build a deck that is 16 feet long and 12 feet wide, with a height of 3 feet. You plan to use 16-inch on-center joist spacing and 5.5-inch wide decking boards. Your chosen beam material allows for a maximum span of 8 feet.

Total Deck Area: 16 ft * 12 ft = 192 sq ft
Linear Feet of Decking: (12 ft * 12 inches/ft / 5.5 inches) * 16 ft * 1.10 (waste) = ~429 linear feet
Estimated 12ft Decking Boards: 429 / 12 = ~36 boards
Number of Joists: (16 ft * 12 inches/ft / 16 inches) + 1 = 13 joists
Number of Beams: 2 (standard for this setup)
Number of Support Posts: (16 ft / 8 ft) * 2 beams = 4 posts
Estimated Post Length: 3 ft (height) + 1 ft (embedment) = 4 feet

This example demonstrates how the calculator provides a quick overview of the materials needed for your deck project. Remember to always verify these estimates with a professional and local building codes.

function calculateDeckMaterials() { var deckLength = parseFloat(document.getElementById("deckLength").value); var deckWidth = parseFloat(document.getElementById("deckWidth").value); var deckHeight = parseFloat(document.getElementById("deckHeight").value); var joistSpacing = parseFloat(document.getElementById("joistSpacing").value); var deckingBoardWidth = parseFloat(document.getElementById("deckingBoardWidth").value); var beamSpan = parseFloat(document.getElementById("beamSpan").value); // Validate inputs if (isNaN(deckLength) || deckLength <= 0 || isNaN(deckWidth) || deckWidth <= 0 || isNaN(deckHeight) || deckHeight <= 0 || isNaN(joistSpacing) || joistSpacing <= 0 || isNaN(deckingBoardWidth) || deckingBoardWidth <= 0 || isNaN(beamSpan) || beamSpan <= 0) { alert("Please enter valid positive numbers for all deck dimensions and specifications."); document.getElementById("result").style.display = "none"; return; } // 1. Total Deck Area var totalDeckArea = deckLength * deckWidth; // 2. Linear Feet of Decking Boards (with 10% waste factor) // Number of boards needed across the width: (deckWidth * 12 inches/ft) / deckingBoardWidth // Total linear feet: (number of boards across width) * deckLength var linearFeetDecking = (deckWidth * 12 / deckingBoardWidth) * deckLength * 1.10; // Add 10% for waste // 3. Number of 12-foot Decking Boards (example length) var numDeckingBoards = Math.ceil(linearFeetDecking / 12); // 4. Number of Joists (assuming joists run perpendicular to length, spanning width) // (deckLength * 12 inches/ft / joistSpacing) + 1 for the end joist var numJoists = Math.ceil((deckLength * 12 / joistSpacing) + 1); // 5. Number of Beams (assuming 2 main beams for a simple rectangular deck, running along the length) var numBeams = 2; // Typically two beams supporting the joists // 6. Number of Support Posts // For each beam, calculate posts needed: Math.ceil(deckLength / beamSpan) // Multiply by numBeams var postsPerBeam = Math.ceil(deckLength / beamSpan); var numPosts = postsPerBeam * numBeams; // 7. Estimated Post Length (add 1 foot for embedment/cutting) var postLength = deckHeight + 1; // Display results document.getElementById("totalDeckArea").innerText = totalDeckArea.toFixed(2); document.getElementById("linearFeetDecking").innerText = linearFeetDecking.toFixed(2); document.getElementById("numDeckingBoards").innerText = numDeckingBoards; document.getElementById("numJoists").innerText = numJoists; document.getElementById("numBeams").innerText = numBeams; document.getElementById("numPosts").innerText = numPosts; document.getElementById("postLength").innerText = postLength.toFixed(1); document.getElementById("result").style.display = "block"; }