Decking Boards Calculator

Deck Length (feet):

Deck Width (feet):

Board Width (inches):

Board Length (feet):

Gap Between Boards (inches):

Waste Factor (%):

Cost Per Board ($):

Enter your deck and board dimensions above and click "Calculate" to see your results.

Understanding Your Decking Board Needs

Building a deck is a rewarding project, but accurately estimating the materials, especially decking boards, is crucial for staying on budget and avoiding delays. Our Decking Boards Calculator simplifies this process by providing a precise estimate based on your specific deck dimensions and board choices.

How to Use the Calculator:

Deck Length (feet): Measure the longest side of your deck area.
Deck Width (feet): Measure the shorter side of your deck area.
Board Width (inches): This is the actual face width of the decking board you plan to use (e.g., a "6-inch" board might actually be 5.5 inches wide). Check the product specifications.
Board Length (feet): The standard length of the decking boards you intend to purchase (e.g., 12 ft, 16 ft).
Gap Between Boards (inches): The recommended spacing between boards for drainage and expansion. A common gap is 1/8 inch (0.125) or 1/4 inch (0.25).
Waste Factor (%): Always account for waste due to cuts, mistakes, or damaged boards. A typical waste factor is 5-15%. For complex decks with many angles, consider a higher percentage.
Cost Per Board ($): Enter the individual cost of one decking board to get an estimated total material cost.

Why a Waste Factor is Important:

The waste factor is a critical component of any material estimation. When cutting boards to fit, you'll inevitably have off-cuts that are too short to be used elsewhere. Additionally, boards can sometimes arrive with minor defects, or mistakes can happen during installation. Including a waste factor ensures you have enough material to complete your project without needing to make extra trips to the store, which can save both time and money in the long run.

Tips for Measuring Your Deck:

Measure twice to ensure accuracy.
For irregular shapes, break the deck into simpler rectangles and calculate each section separately, then sum the results.
Consider the direction you want your boards to run. This calculator assumes boards run parallel to the deck's length, covering its width. If you plan to run them the other way, simply swap your length and width inputs.

Example Calculation:

Let's say you have a deck that is 12 feet long and 10 feet wide. You're using boards that are 5.5 inches wide and 12 feet long, with a 0.25-inch gap between them. You want to include a 10% waste factor, and each board costs $15.

Deck Width in inches: 10 ft * 12 in/ft = 120 inches
Effective Board Coverage (Board Width + Gap): 5.5 in + 0.25 in = 5.75 inches
Number of boards needed across the width: ceil(120 inches / 5.75 inches) = ceil(20.87) = 21 boards
Total linear feet required: 21 boards * 12 ft/board = 252 linear feet
Raw number of boards: 252 linear feet / 12 ft/board = 21 boards
Boards with waste: 21 boards * (1 + 10/100) = 21 * 1.1 = 23.1 boards
Final Number of Boards (rounded up): 24 boards
Estimated Total Cost: 24 boards * $15/board = $360

Using this calculator will help you get a clear picture of your material needs, making your deck building project smoother and more predictable.

function calculateDecking() { var deckLengthFeet = parseFloat(document.getElementById('deckLength').value); var deckWidthFeet = parseFloat(document.getElementById('deckWidth').value); var boardWidthInches = parseFloat(document.getElementById('boardWidth').value); var boardLengthFeet = parseFloat(document.getElementById('boardLength').value); var gapWidthInches = parseFloat(document.getElementById('gapWidth').value); var wasteFactorPercent = parseFloat(document.getElementById('wasteFactor').value); var costPerBoard = parseFloat(document.getElementById('costPerBoard').value); var resultDiv = document.getElementById('deckingResult'); // Input validation if (isNaN(deckLengthFeet) || deckLengthFeet <= 0 || isNaN(deckWidthFeet) || deckWidthFeet <= 0 || isNaN(boardWidthInches) || boardWidthInches <= 0 || isNaN(boardLengthFeet) || boardLengthFeet <= 0 || isNaN(gapWidthInches) || gapWidthInches < 0 || isNaN(wasteFactorPercent) || wasteFactorPercent < 0 || isNaN(costPerBoard) || costPerBoard < 0) { resultDiv.innerHTML = 'Please enter valid positive numbers for all fields.'; return; } // Convert deck width to inches for consistent calculation with board width and gap var deckWidthInches = deckWidthFeet * 12; // Calculate effective width of one board including the gap it occupies var boardWidthWithGapInches = boardWidthInches + gapWidthInches; // Calculate the number of boards needed to cover the deck's width // We use Math.ceil because even a small fraction of a board means you need a whole new board var numBoardsAcrossWidth = Math.ceil(deckWidthInches / boardWidthWithGapInches); // Calculate the total linear feet of boards required var totalLinearFeetRequired = numBoardsAcrossWidth * deckLengthFeet; // Calculate the raw number of individual boards needed before waste var rawNumBoards = totalLinearFeetRequired / boardLengthFeet; // Apply the waste factor var wasteMultiplier = 1 + (wasteFactorPercent / 100); var boardsWithWaste = rawNumBoards * wasteMultiplier; // Round up to the nearest whole board, as you can't buy fractions of boards var finalNumBoards = Math.ceil(boardsWithWaste); // Calculate total estimated cost var totalCost = finalNumBoards * costPerBoard; // Display results resultDiv.innerHTML = '

Your Decking Board Estimate:

' + 'Total Deck Area: ' + (deckLengthFeet * deckWidthFeet).toFixed(2) + ' sq ft' + 'Number of Boards Needed: ' + finalNumBoards + ' boards' + 'Estimated Total Cost: $' + totalCost.toFixed(2) + '' + '(Includes ' + wasteFactorPercent + '% waste factor and rounded up to the nearest whole board)'; }