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How to Calculate the Amount of James Hardie Siding You Need

Jun 12, 2024

When it comes to home renovation, choosing the right materials can significantly impact both the aesthetics and durability of your property. James Hardie siding, renowned for its strength and appealing finish, is a popular choice among homeowners. However, determining how much siding you need can be a challenge. This guide will walk you through the steps to accurately measure and calculate the necessary siding for your home.

Understanding Siding Measurements

amount of james hardie siding you need

James Hardie siding is favored for its resilience against weather elements and its ability to mimic the look of real wood without the maintenance hassles. Before purchasing, it’s essential to understand how siding is measured. Typically, siding is sold by the square, where one square covers 100 square feet. Knowing this will help you better calculate how much material you need.

Tools and Materials Required

To start, you’ll need a few tools:

  • Tape measure
  • Calculator
  • Notepad or digital device for recording measurements
  • Ladder (for measuring heights safely)

Step-by-Step Calculation Process

Measuring Your Home’s Exterior

  1. Measure the Width and Height of Each Wall: For each wall, measure both the width and height in feet. Multiply these numbers together to get the square footage of each wall.
  2. Account for Windows and Doors: Measure the width and height of each window and door. Multiply to find the area and subtract these from the wall’s total square footage.
  3. Add All Wall Measurements Together: Sum the adjusted square footages of all walls to get the total square footage that needs covering.

Determining How Much Siding is Required

To find out how much James Hardie siding you’ll need, take the total square footage of your walls and divide it by 100 (as each square of siding covers 100 square feet). Always round up to ensure you have enough material, and consider purchasing a little extra to account for mistakes or unique architectural features.

Additional Tips for Accurate Measurements

Consider the Overlap

James Hardie siding panels are designed to overlap. It’s important to consider this overlap in your calculations, as it can affect the total amount of siding you need. Generally, an additional 10% is a safe estimate for the overlap.

Check for Unique Features

Features such as gables or eaves require special attention when measuring. For gables, measure the width at the base and the height from the base to the peak, then multiply these together and divide by two to find the area of the triangle.


amount of james hardie siding you need

Calculating the amount of siding needed for your home doesn’t have to be complicated. With the right tools and a careful approach, you can determine how much James Hardie siding will effectively cover your home. Remember to double-check your measurements, consider the overlap, and always round up to ensure you won’t run short. Taking the time to do it right will help ensure that your home renovation looks great and lasts for years.

If you have any questions or need further assistance, feel free to contact Johnson County Siding & Window today. We’re here to help you ensure your renovation goes smoothly with the perfect amount of siding.


If you know you want to get your home exterior project done, but are feeling stress about paying for it all at once, we can help.

Our financing partner, GreenSky, has sensible payment plans that work for homeowners who prefer to pay in installments. You can also ask your JoCo Siding & Window Co. sales representative about the details!

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Johnson County Siding & Window Co.
"Working with Johnson County Siding & Windows was a pleasure. They delivered high quality work swiftly for a reasonable price and were respectful of my home. Highly recommend Johnson County Siding & Windows for window replacement!”

- David D.
Johnson County Siding & Window Co.
"Everyone associated with the company was professional and respectful. Our windows look great, communication was very good, and the time line was manageable. Would recommend!”

- Sheri C.
Johnson County Siding & Window Co.
"We are impressed with the quality of the work and we are very pleased with the value after comparing to other options. The crew that did the siding was absolutely awesome. And we are thrilled with the James Hardie Color Plus Siding for the low maintenance from here on out! Thank you to everyone at Johnson County Siding & Window from their sales person to their lead manager and to the crew!”

- Sharon M.

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