Block Calculator

Wall Length (feet):

Wall Height (feet):

Block Length (inches):

Block Height (inches):

Mortar Joint Thickness (inches):

Waste Percentage (%):

Enter values and click "Calculate Blocks" to see the results.

function calculateBlocks() { var wallLength = parseFloat(document.getElementById('wallLength').value); var wallHeight = parseFloat(document.getElementById('wallHeight').value); var blockLength = parseFloat(document.getElementById('blockLength').value); var blockHeight = parseFloat(document.getElementById('blockHeight').value); var mortarThickness = parseFloat(document.getElementById('mortarThickness').value); var wastePercentage = parseFloat(document.getElementById('wastePercentage').value); var resultDiv = document.getElementById('result'); if (isNaN(wallLength) || isNaN(wallHeight) || isNaN(blockLength) || isNaN(blockHeight) || isNaN(mortarThickness) || isNaN(wastePercentage) || wallLength <= 0 || wallHeight <= 0 || blockLength <= 0 || blockHeight <= 0 || mortarThickness < 0 || wastePercentage < 0) { resultDiv.innerHTML = 'Please enter valid positive numbers for all fields.'; return; } // Convert block dimensions and mortar thickness to feet for consistent units var blockLengthFeet = blockLength / 12; var blockHeightFeet = blockHeight / 12; var mortarThicknessFeet = mortarThickness / 12; // Calculate effective block dimensions including mortar joints var effectiveBlockLengthFeet = blockLengthFeet + mortarThicknessFeet; var effectiveBlockHeightFeet = blockHeightFeet + mortarThicknessFeet; // Calculate wall area var wallAreaSqFt = wallLength * wallHeight; // Calculate the area covered by one block including its mortar joints var blockAreaSqFt = effectiveBlockLengthFeet * effectiveBlockHeightFeet; // Calculate the raw number of blocks needed var rawBlocksNeeded = wallAreaSqFt / blockAreaSqFt; // Add waste percentage var blocksWithWaste = rawBlocksNeeded * (1 + wastePercentage / 100); // Round up to the nearest whole block as you can't buy partial blocks var totalBlocksNeeded = Math.ceil(blocksWithWaste); // Calculate blocks per row and number of rows for additional info var blocksPerRow = Math.ceil(wallLength / effectiveBlockLengthFeet); var numberOfRows = Math.ceil(wallHeight / effectiveBlockHeightFeet); resultDiv.innerHTML = '

Calculation Results

' + 'Total Wall Area: ' + wallAreaSqFt.toFixed(2) + ' sq ft' + 'Blocks per Horizontal Row: ' + blocksPerRow + " + 'Number of Vertical Rows: ' + numberOfRows + " + 'Total Blocks Required (including ' + wastePercentage + '% waste): ' + totalBlocksNeeded + "; }

Understanding the Block Calculator

Whether you're planning a new garden wall, a foundation, or a structural building, accurately estimating the number of blocks you'll need is crucial. The Block Calculator helps you determine the precise quantity of blocks required for your project, saving you time, money, and potential headaches from under or over-ordering materials.

How It Works

This calculator takes into account the dimensions of your wall and the specific blocks you plan to use, along with essential factors like mortar joint thickness and waste percentage. Here's a breakdown of the inputs:

Wall Length (feet): The total horizontal length of the wall you intend to build.
Wall Height (feet): The total vertical height of the wall.
Block Length (inches): The length of a single block. Common concrete blocks are often 16 inches long.
Block Height (inches): The height of a single block. Common concrete blocks are often 8 inches high.
Mortar Joint Thickness (inches): The thickness of the mortar layer between blocks. A standard mortar joint is typically 3/8 inch (0.375 inches). This is critical because it adds to the effective size of each block.
Waste Percentage (%): An essential factor to account for breakage, cutting errors, or future repairs. It's always wise to order a little extra. A typical waste percentage for blockwork can range from 5% to 15%, with 10% being a common recommendation for most projects.

Why is Mortar Joint Thickness Important?

Many people forget to account for the mortar when calculating block quantities. While a single block might be 16×8 inches, once you add a 3/8-inch mortar joint on all sides, the effective area each block covers is slightly larger. The calculator incorporates this to provide a more accurate count, preventing you from ordering too many or too few blocks.

The Role of Waste Percentage

Construction projects rarely go exactly as planned. Blocks can break during transport or handling, some might need to be cut to fit specific sections, and mistakes can happen. Including a waste percentage ensures you have enough material to complete the job without delays caused by re-ordering. For example, if the calculator suggests 100 blocks and you add a 10% waste, it will recommend ordering 110 blocks.

Example Calculation

Let's say you want to build a wall that is 20 feet long and 8 feet high using standard concrete blocks that are 16 inches long and 8 inches high. You plan for a 0.375-inch mortar joint and a 10% waste factor.

Wall Area: 20 ft * 8 ft = 160 sq ft
Block Dimensions in Feet: Length = 16/12 = 1.333 ft, Height = 8/12 = 0.667 ft
Mortar Thickness in Feet: 0.375/12 = 0.03125 ft
Effective Block Length (with mortar): 1.333 ft + 0.03125 ft = 1.36425 ft
Effective Block Height (with mortar): 0.667 ft + 0.03125 ft = 0.69825 ft
Area per Block (with mortar): 1.36425 ft * 0.69825 ft = 0.9527 sq ft
Raw Blocks Needed: 160 sq ft / 0.9527 sq ft/block = 167.94 blocks
Blocks with 10% Waste: 167.94 * (1 + 10/100) = 167.94 * 1.10 = 184.73 blocks
Total Blocks (rounded up): You would need to order 185 blocks.

Using the Block Calculator simplifies this process, providing you with an instant and accurate estimate for your construction project.