Siding Calculator

Installing new siding is a major home improvement project that can dramatically boost your home's curb appeal, improve its weather resistance, and even increase its value. Proper planning is essential, and the first step is to accurately calculate the amount of siding material you'll need. Our Siding Calculator is a practical tool designed to help you estimate the number of planks and the total "squares" of siding required to cover your home's exterior walls. This ensures you can get accurate quotes from contractors and purchase the right amount of material for your project.

How to Use the Siding Calculator

Estimating your siding material needs is a simple process:

1. Select Units: Choose your preferred measurement system, either imperial (feet/inches) or metric (meters/cm).
2. Enter Total Wall Area: Input the total square footage (or square meters) of the exterior walls you plan to cover. You'll need to calculate this separately.
3. Enter Plank Dimensions: Provide the "Plank Exposure" (the visible height of one installed plank) and the "Plank Length."
4. Set Waste Factor: Enter a percentage for waste. 10-15% is standard to account for cuts around windows, doors, and gables.
5. Calculate Materials: Click the "Calculate Siding" button to see the estimated number of planks and total squares of siding needed.

How Siding Quantity is Calculated

The calculator first determines your total material need, including waste, and then divides that by the coverage area of a single plank.

1. Calculate Total Area with Waste

First, the waste factor percentage is applied to your total wall area. You can never just order the exact square footage of your walls, as a significant amount of material is lost to cuts.

Total Area Needed = Wall Area × (1 + Waste Factor %)

2. Calculate Single Plank Coverage

The coverage area of a single plank is determined by its length multiplied by its "exposure." The exposure is the height of the plank that is visible after it has been installed and lapped over by the course above it. This is always less than the plank's full width.

Plank Coverage = Plank Exposure × Plank Length

3. Find Total Planks

Finally, the total area needed is divided by the coverage of a single plank to find the total number of planks required, rounding up to the nearest whole number.

How to Measure Your Home's Wall Area

The most crucial input for this calculator is the total wall area.

1. Measure Each Wall: For each exterior wall, measure its length and height. Multiply them to get the area of that wall.
2. Handle Gables: For the triangular gable ends under the roof, use the formula for the area of a triangle: (Base × Height) / 2.
3. Add All Areas: Sum the areas of all the rectangular walls and triangular gables to get your total gross wall area.
4. Subtract Openings: Now, subtract the area of all major openings that will not be covered with siding, such as windows, doors, and garage doors.

The final number after subtracting openings is the "Total Wall Area" you should enter into the calculator.

Important Terms in Siding

• Square: In the exterior construction industry (for both roofing and siding), a "square" is a unit of area equal to 100 square feet. Siding materials are often priced and sold by the square.
• Exposure: The visible height of a siding plank once it's installed. A lap siding plank might be 6 inches wide in total, but if it's installed with a 1-inch overlap, its exposure is only 5 inches. This is the number you must use for an accurate calculation.
• Course: A single horizontal row of siding planks.

Frequently Asked Questions