Deck Boards Calculator

Deck Board Calculator

(e.g., 5.5 for a nominal 6-inch board)

(e.g., 0.125 for 1/8″, 0.25 for 1/4″)

(e.g., 12, 16, 20)

(e.g., 5-10% for cuts, mistakes)

function calculateDeckBoards() { var deckLengthFeet = parseFloat(document.getElementById('deckLengthFeet').value); var deckWidthFeet = parseFloat(document.getElementById('deckWidthFeet').value); var boardWidthInches = parseFloat(document.getElementById('boardWidthInches').value); var boardGapInches = parseFloat(document.getElementById('boardGapInches').value); var boardLengthFeet = parseFloat(document.getElementById('boardLengthFeet').value); var wasteFactorPercent = parseFloat(document.getElementById('wasteFactorPercent').value); // Input validation if (isNaN(deckLengthFeet) || deckLengthFeet <= 0 || isNaN(deckWidthFeet) || deckWidthFeet <= 0 || isNaN(boardWidthInches) || boardWidthInches <= 0 || isNaN(boardGapInches) || boardGapInches < 0 || isNaN(boardLengthFeet) || boardLengthFeet <= 0 || isNaN(wasteFactorPercent) || wasteFactorPercent < 0) { document.getElementById('totalLinearFeetNeeded').innerText = 'Total Linear Feet Needed: Please enter valid positive numbers for all fields.'; document.getElementById('boardsToPurchase').innerText = 'Number of Boards to Purchase: –'; return; } // 1. Convert deck width to inches var deckWidthInches = deckWidthFeet * 12; // 2. Calculate effective width per board (board + gap) var effectiveBoardWidth = boardWidthInches + boardGapInches; // 3. Number of board "rows" needed across the deck width // We round up to ensure full coverage var numRows = Math.ceil(deckWidthInches / effectiveBoardWidth); // 4. Total linear feet of boards required (before waste) var totalLinearFeetRaw = numRows * deckLengthFeet; // 5. Apply waste factor var totalLinearFeetWithWaste = totalLinearFeetRaw * (1 + wasteFactorPercent / 100); // 6. Number of individual boards to purchase // Round up to the nearest whole board as you can't buy fractions of boards var numBoardsToPurchase = Math.ceil(totalLinearFeetWithWaste / boardLengthFeet); document.getElementById('totalLinearFeetNeeded').innerText = 'Total Linear Feet Needed: ' + totalLinearFeetWithWaste.toFixed(2) + ' linear feet'; document.getElementById('boardsToPurchase').innerText = 'Number of Boards to Purchase: ' + numBoardsToPurchase + ' boards (' + boardLengthFeet + ' ft each)'; }

Understanding Your Deck Board Needs

Building a deck is an exciting project, and accurately estimating the materials needed is crucial for staying on budget and avoiding delays. Our Deck Board Calculator helps you determine exactly how many deck boards you'll need for your project, taking into account common factors like board width, spacing, and waste.

How the Calculator Works

This tool simplifies the complex task of material estimation by breaking it down into a few key inputs:

• Deck Length (feet): The total length of your deck.
• Deck Width (feet): The total width of your deck.
• Actual Board Width (inches): This is the true width of the deck board, which is often slightly less than its nominal size. For example, a "6-inch" deck board is typically 5.5 inches wide. Measuring an actual board is recommended.
• Board Gap (inches): The spacing you plan to leave between each deck board for drainage and expansion. Common gaps range from 1/8 inch (0.125″) to 1/4 inch (0.25″).
• Board Length (feet): The standard length of the boards you intend to purchase (e.g., 12, 16, or 20 feet).
• Waste Factor (%): An essential percentage added to account for cuts, mistakes, damaged boards, or future repairs. A typical waste factor is between 5% and 10%.

The Calculation Process

The calculator performs the following steps:

1. It converts your deck's width into inches.
2. It calculates the "effective width" of each board by adding the actual board width to the desired gap.
3. It determines how many rows of boards are needed to cover the entire width of your deck, rounding up to ensure full coverage.
4. It then multiplies the number of rows by the deck's length to get the total linear feet of decking required.
5. A waste factor is applied to this total to give you a more realistic quantity.
6. Finally, it divides the total linear feet (with waste) by the length of the individual boards you plan to buy, rounding up to the nearest whole board, as you cannot purchase partial boards.

Example Scenario

Let's say you're building a deck that is 10 feet long and 8 feet wide. You plan to use boards that are 5.5 inches wide (actual measurement) and 16 feet long. You want a 0.25-inch gap between boards and will add a 10% waste factor.

• Deck width in inches: 8 feet * 12 inches/foot = 96 inches.
• Effective board width: 5.5 inches (board) + 0.25 inches (gap) = 5.75 inches.
• Number of board rows needed: 96 inches / 5.75 inches/row = 16.69 rows. Rounded up, this is 17 rows.
• Total linear feet (raw): 17 rows * 10 feet/row = 170 linear feet.
• Total linear feet with waste: 170 linear feet * (1 + 10/100) = 170 * 1.10 = 187 linear feet.
• Number of individual boards to purchase: 187 linear feet / 16 feet/board = 11.6875 boards. Rounded up, you would need to purchase 12 boards.

Using this calculator helps ensure you have enough material to complete your deck project efficiently and without unexpected trips to the lumberyard.