How to Measure for Siding

By Amanda Lutz Updated May 8, 2024

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Installing new siding is a significant home improvement project that requires plenty of planning. It’s important to know precisely how much siding you’ll need, whether you plan to install the siding yourself or hire a contractor. We’ll walk you through how to measure for siding for your home’s exterior in our comprehensive guide below.

What Is Siding?

Siding is a protective material that encases your home’s exterior wherever there aren’t brick walls. It’s typically arranged in horizontal or vertical panels and you might find it around your home’s windows and doorways, near gable roofs, and surrounding the garage door.

Siding protects your home from the elements, pests, and potential impact damages. It rests atop layers of sheathing and moisture barriers and stands as the primary defense against rain, snow, wind, and other potential hazards.

There are many different types of siding material. Consider these popular options:

Knowing the dimensions of existing siding panels could help you make accurate estimates about hard-to-reach areas. In that case, you’ll be able to calculate the area of less-accessible sections rather than struggling to measure them.

Siding Measuring Process

It’s important to know the dimensions of the area that needs to be covered with siding before you begin replacing it. You’ll need to place a second order if you order too little, which could lead to delays or poor color-matching. If you order too much, you’ll have a lot of expensive waste.

Measuring for siding is simple and requires only a few tools.

Tools Required to Measure Siding

Have these tools ready when you want to measure for siding on your home or a detached garage:

Step-by-Step Measuring Guide

Follow our step-by-step guide to measuring siding, and you’ll be unlikely to miscalculate or forget about sections around your home:

  1. Measure the rectangular wall sections: These are the largest sections and the easiest ones to measure. Start at the front of your house, listing and measuring each rectangular patch of siding. Measure the width and height, and then multiply them together. Don’t subtract the area of standard-sized windows from the total area. Jot down each individual section’s area, and add them all together in a separate column.
  2. Measure the triangular gables: Gable roof sections have triangular patches of siding under the eaves. Measure the width of each, multiply it by their heights, and multiply the product by 0.75. Add up the sections.
  3. Double-check the perimeter of your home: Look for sections of siding that are awkwardly sized or sit in areas that are difficult to access. This includes sections around your patio door or bay windows, dormers, and detached garages.
  4. Add up the accents: Start by adding up the corner posts, which are the interior and exterior corners around the outside of your home. If any of these corner edges are longer than 12 feet, then add an additional corner piece to your total count. You’ll also need to measure the perimeter of trim or J-channels around all four sides of your windows and doors to calculate the needed amount of trim.
  5. Calculate how much starter strip you need: Measure the length of the bottom of each siding section that you plan to install. This may be the perimeter of your exterior, a little more, or a little bit less.

By the end of this process, you should have recorded separate measurements for each section of siding, each type of siding, and each type of trim piece. You’ll also need three cumulative numbers: the total surface area of siding panels, the total number of corner pieces, and the total linear footage of trim. Having secured this data, you can start calculating the siding squares of siding you need.

What Are Siding Squares?

You order siding in units called “squares” rather than in square feet. One siding square is equivalent to 100 square feet.

That amount of siding won’t need to be in 10-foot by 10-foot sections, though, since the siding may come in different dimensions. Siding that’s 12 inches wide may include 100 linear feet of siding per square, for example, while siding that’s 6 inches wide may include 200 linear feet. By calculating your total needs as squares, you can more easily compare prices between different sizes, styles, and materials.

The only variables you must consider are corner pieces and trim, which are usually measured in linear feet. Simply add up the number of pieces you need, or the total length in feet, before placing your order.

Estimating the Amount of Siding Needed

Remember that you can only estimate the amount of siding you need, even if you measure in exact detail. It’s impossible to measure down to the square inch. Consider the variables below as you measure.

Some of these factors will increase the amount of siding you need while others will decrease it. This is why there are a few best practices for estimating your siding needs.

To start, multiply the length and height of triangular sections by 0.75 instead of by 0.5, which is the standard for conventional triangle formulas. This gives some wiggle room to help you work around diagonal cuts and small pieces.

Consider getting up to 10% extra siding compared to what you think is needed, especially for custom orders with unique colors. This gives you a bit of room for error. If you order too little of a custom color, you may not get an exact match when you go back and buy more.

Finally, consider what to do if you order too much siding. Some homeowners keep excess siding, especially if they’re thinking about building a shed, putting new siding on a detached garage, or worrying about hailstorms and tornado damage. If you order a standard color and style, though, you may be able to return unused panels or sell them back to the contractor.

Common Mistakes When Measuring for Siding

Measuring for siding can be complicated. It’s easy to accidentally skip over sections, miscalculate square footage, or add up totals incorrectly.

Be cautious of making these common errors when measuring your home’s siding:

Our Recommendation

Knowing how to measure for siding is a crucial first step in siding replacement, whether it’s a do-it-yourself (DIY) project or you hire a contractor. Carefully measure your home’s exterior and convert the total square footage you need into squares. Remember to add up the corner pieces and starter strips for the project, too. When you know the needed amount of material you can finalize your budget, place an order, and stay on top of contractors’ estimates for material costs.

How to Measure for Siding FAQ

How do I calculate how much siding I need?

Calculate how much siding you need by measuring the height and length of each section of siding around your home’s exterior. For rectangular sections, multiply the height by the length; for triangular sections, multiply the product of the height and length by 0.75. Add up all the sections and convert them to squares.

How do you measure a piece of siding?

Measure a piece of siding by multiplying the length of a panel by its height, which yields its square footage.

How many square feet is a box of siding?

How many square feet are in a box of siding depends on the material and the size of each panel. Each box typically amounts to one siding square (100 square feet) or two siding squares (200 square feet).

How do you quote for a siding job?

A quote for a siding job typically includes costs for the siding materials, the cost of trim and accents, the price of additional materials such as caulk and nails, the cost of labor, and any taxes included in the bill.

What is a siding square and why is it important?

A siding square is a standard siding measurement of 100 square feet. This is important because panels of different sizes may have varying linear feet per 100 square feet of covered area. By measuring siding in squares, you can more easily compare prices and place the right order.