How to Calculate How Much Siding I Need

Siding Material Estimator

Wall Measurements (in feet):

Wall 1 Length:

Wall 1 Height:

Wall 2 Length:

Wall 2 Height:

Wall 3 Length:

Wall 3 Height:

Wall 4 Length:

Wall 4 Height:

Openings & Waste Factor:

Number of Standard Windows (approx. 15 sq ft each):

Number of Standard Doors (approx. 21 sq ft each):

Waste Factor (%):

Calculation Results:

Total Wall Area: — sq ft

Total Openings Area: — sq ft

Net Siding Area Required: — sq ft

Siding Area with Waste: — sq ft

Number of Siding Squares Needed: — squares

function calculateSiding() { var wall1Length = parseFloat(document.getElementById('wall1Length').value) || 0; var wall1Height = parseFloat(document.getElementById('wall1Height').value) || 0; var wall2Length = parseFloat(document.getElementById('wall2Length').value) || 0; var wall2Height = parseFloat(document.getElementById('wall2Height').value) || 0; var wall3Length = parseFloat(document.getElementById('wall3Length').value) || 0; var wall3Height = parseFloat(document.getElementById('wall3Height').value) || 0; var wall4Length = parseFloat(document.getElementById('wall4Length').value) || 0; var wall4Height = parseFloat(document.getElementById('wall4Height').value) || 0; var numWindows = parseFloat(document.getElementById('numWindows').value) || 0; var numDoors = parseFloat(document.getElementById('numDoors').value) || 0; var wasteFactor = parseFloat(document.getElementById('wasteFactor').value) || 0; // Standard opening sizes (can be adjusted) var standardWindowArea = 15; // sq ft var standardDoorArea = 21; // sq ft var squareFootPerSquare = 100; // 1 siding square = 100 sq ft // Calculate total wall area var totalWallArea = (wall1Length * wall1Height) + (wall2Length * wall2Height) + (wall3Length * wall3Height) + (wall4Length * wall4Height); // Calculate total area of openings var totalOpeningsArea = (numWindows * standardWindowArea) + (numDoors * standardDoorArea); // Calculate net siding area required var netSidingArea = totalWallArea – totalOpeningsArea; if (netSidingArea < 0) { netSidingArea = 0; // Cannot have negative siding area } // Apply waste factor var sidingWithWaste = netSidingArea * (1 + (wasteFactor / 100)); // Calculate number of siding squares needed (round up) var sidingSquares = Math.ceil(sidingWithWaste / squareFootPerSquare); // Display results document.getElementById('totalWallArea').innerText = 'Total Wall Area: ' + totalWallArea.toFixed(2) + ' sq ft'; document.getElementById('totalOpeningsArea').innerText = 'Total Openings Area: ' + totalOpeningsArea.toFixed(2) + ' sq ft'; document.getElementById('netSidingArea').innerText = 'Net Siding Area Required: ' + netSidingArea.toFixed(2) + ' sq ft'; document.getElementById('sidingWithWaste').innerText = 'Siding Area with Waste: ' + sidingWithWaste.toFixed(2) + ' sq ft'; document.getElementById('sidingSquares').innerText = 'Number of Siding Squares Needed: ' + sidingSquares + ' squares'; }

How to Calculate How Much Siding You Need

Estimating the correct amount of siding for your home is a crucial step in any exterior renovation project. Ordering too little can cause delays and additional shipping costs, while ordering too much leads to unnecessary expenses and waste. This guide, along with our Siding Material Estimator, will help you accurately determine your material needs.

Understanding Siding Measurements

Siding is typically measured in square feet (sq ft) and often sold in "squares." One siding square is equivalent to 100 square feet. This unit simplifies large-scale material ordering.

Step-by-Step Siding Calculation

Step 1: Measure Each Wall

The most fundamental part of siding estimation is measuring the area of each exterior wall. For rectangular walls, this is straightforward:

Measure the length of the wall (in feet).
Measure the height of the wall (in feet).
Multiply length by height to get the square footage for that wall.
Repeat this for all walls of your house.

Example: A wall that is 20 feet long and 10 feet high has an area of 200 sq ft (20 x 10).

For Gables and Irregular Shapes:

Gables (Triangular Walls): Measure the base (width of the wall) and the height (from the base to the peak). The area is (Base x Height) / 2.
Other Irregularities: Break down complex shapes into simpler rectangles and triangles, calculate each area, and add them together.

Our calculator provides inputs for up to four walls. If you have more, or complex shapes like gables, calculate their areas separately and add them to one of the wall area inputs, or sum them up manually before using the calculator.

Step 2: Calculate Total Wall Area

Sum the square footage of all your walls (including gables and any other exterior surfaces that will be sided). This gives you the gross total area.

Example: If you have four walls: 200 sq ft, 300 sq ft, 200 sq ft, and 300 sq ft, your total wall area is 1000 sq ft.

Step 3: Subtract Openings (Windows and Doors)

You won't be siding over windows and doors, so their areas need to be subtracted from the total wall area. For accurate results:

Measure the height and width of each window and door.
Calculate the square footage for each (Height x Width).
Sum the areas of all windows and doors.

Our calculator uses standard estimates (15 sq ft for a window, 21 sq ft for a door) for convenience. If your openings vary significantly, measure them individually and adjust your calculations accordingly, or use the calculator's inputs for the number of standard openings and then manually subtract any custom opening areas from the 'Total Wall Area' before inputting, or add them as negative values to one of the wall areas.

Example: If you have 6 standard windows (6 x 15 sq ft = 90 sq ft) and 2 standard doors (2 x 21 sq ft = 42 sq ft), your total opening area is 132 sq ft.

Net Siding Area: Subtract the total opening area from the total wall area. (1000 sq ft – 132 sq ft = 868 sq ft).

Step 4: Add a Waste Factor

It's almost impossible to install siding without some waste due to cuts, mistakes, damaged pieces, or future repairs. A waste factor is a percentage added to your net siding area to account for this. Common waste factors range from 5% to 15%, depending on the complexity of your home's design and your experience level.

Simple, rectangular homes: 5-10% waste factor.
Homes with many windows, doors, gables, or complex angles: 10-15% waste factor.

Example: With a net siding area of 868 sq ft and a 10% waste factor: 868 sq ft * 1.10 = 954.8 sq ft.

Step 5: Convert to Siding Squares

Once you have the total siding area with the waste factor included, divide this number by 100 to get the number of siding squares needed. Always round up to the nearest whole number, as you cannot buy partial squares.

Example: 954.8 sq ft / 100 = 9.548 squares. Rounded up, you would need 10 siding squares.

Using the Siding Material Estimator

Our calculator simplifies these steps:

Enter the length and height for each of your main walls. If you have fewer than four walls, leave the unused fields at 0.
Input the number of standard windows and doors.
Enter your desired waste factor percentage.
Click "Calculate Siding Needed" to get your estimated total square footage and the number of siding squares required.

Always double-check your measurements and consider consulting with a professional siding installer for complex projects to ensure the most accurate estimate.