How to Measure Square Footage for Siding?

To measure square footage for siding, calculate the surface area of each wall while subtracting openings like doors and windows, then add extra for waste. This ensures you order enough material and account for cuts and imperfections.

Measuring for siding is an important first step in any reclaimed wood siding project. The goal is to accurately calculate the surface area you want to cover by separating the building into sections and accounting for windows, roofs, doors, and overages.

If you’re using reclaimed wood siding, it’s important to understand that no two boards are exactly alike. Each piece has its own character—shaped by years of exposure, use, and weather. This natural variation adds visual richness and depth to the final installation, but it also means you’re working with a material that’s less uniform than new lumber.

This post walks you through how to estimate how much siding you’ll need. It covers each step—from gathering tools to dividing your building into measurable sections, calculating total wall surface area, and subtracting for windows, doors, and roofs. Along the way, we’ll point out special considerations as “Tips” for measuring for reclaimed wood. Whether you’re a homeowner planning a renovation or a contractor estimating materials for a job, this guide provides a clear, practical approach to measuring accurately and preparing for a successful siding installation.

Overview: Estimating in 3 Key Steps

Calculate the square footage of your exterior walls (Steps 1-3)

Subtract the square footage of doors and windows (Step 4)

Add 10–15% extra to account for trimming and installation waste (Step 5)

Step 1: Gather Your Tools

Before measuring for siding, get organized. Accurate siding estimates depend on reliable measurement, so having the right tools on hand will make the job faster, safer, and more precise. Whether you’re measuring a single wall or a multi-story home, preparation is key. Taking the time to set yourself up properly reduces the chances of errors, missed sections, or having to redo measurements later. Starting with the right gear  will help ensure that you get an accurate result.

You’ll need:

• Tape measure – Both retractable and folding are useful
• A notepad or smartphone for notes
• E&K Vintage Woods Siding Square Feet Calculator
• A ladder for hard-to-reach areas

Step 2: Understand the Basics of Surface Area

Wall area is just length times height—a simple formula. But buildings aren’t always simple rectangles, so you’ll often need to break the structure into smaller, manageable sections. This might mean treating gable ends as triangles, dividing complex facades into multiple rectangles, or isolating bump-outs and recessed areas. By simplifying the geometry, you can apply basic math to get an accurate total without guesswork. It’s a little extra effort upfront, but it pays off in making wood order estimations.

• Main walls: measure width × height
• Gable ends: treat as triangles (base × height ÷ 2)
• Windows/doors: subtract their area (only large ones)

Tip: If it feels like geometry class, it kind of is. But simple geometry: rectangles and triangles.

Step 3: Measure the Walls

Start with your building’s main walls when measuring for siding. These are usually the largest and most straightforward surfaces to measure. Begin at one corner and work your way around, recording the width and height of each wall section. For multi-story buildings, measure each level separately if the heights vary. Be sure to account for any changes in elevation or architectural features that interrupt the wall surface. Keeping your measurements organized by section helps streamline your calculations and makes it easier to subtract openings or irregular features.

Example:

• Rectangle area= base width x height
• Width: 30 feet
• First floor height: 15 feet
• Second floor height: 15 feet
• Total rectangular wall: 30 ft × 30 ft = 900 sq ft

Now tackle any gable ends. These sections are usually triangular, found above the main wall under the roof peak. To calculate the area, use the standard triangle formula: base times height divided by two. The base is typically the same as the wall width below, and the height runs from the top of the wall to the roof peak. Measuring these accurately ensures you don’t underestimate the total surface area—especially important if your design includes multiple gables.

• Triangle area = base × height ÷ 2
• Base = 30 feet
• Height = 6 feet
• Gable area: (30 × 6) ÷ 2 = 90 sq ft
• So far, total = 900 + 90 = 990 sq ft

Break larger walls into sections if needed. This is especially helpful if the wall has multiple heights or features like chimneys or balconies. Treat each section as its own rectangle or triangle, measure it individually, and write everything down clearly.

Tip: Measure twice. Record everything.

Step 4: Subtract Windows and Doors

No sense siding over windows and doors—they won’t need material, so be sure to subtract them from your total. Measure the height and width of each large window and door, calculate the area, and subtract that from the wall section it’s in. You can usually ignore small openings, as trim and layout will cover minor differences. This step helps you avoid overestimating and keeps your material order accurate.

Example:

• Two top-floor windows: 6 ft × 3 ft = 18 sq ft × 2 = 36 sq ft
• Two bottom-floor windows: 5 ft × 6 ft = 30 sq ft × 2 = 60 sq ft
• One door: 3 ft × 7 ft = 21 sq ft
• Total to subtract: 36 + 60 + 21 = 117 sq ft
• 990 – 117 = 873 sq ft of siding needed

Tip: Small or medium windows? Ignore them. The amount of wood will not dramatically affect the total

Step 5: Add Extra Material for Waste When Measuring for Siding

Don’t cut it too close. You need extra material for several practical reasons. Boards may need to be trimmed to fit around windows, corners, and architectural details, and mistakes or unexpected cuts happen even on well-planned jobs. In the case of reclaimed wood, some boards might have character marks you choose not to use. You’ll also want flexibility to maintain consistent patterns and align seams cleanly. We recommend adding 10%-15%  overage to your total square footage. It’s a small buffer that can save time, money, and frustration down the line.

• Cutting mistakes
• Pattern matching
• Unexpected defects

Example:

• 873 sq ft becomes:
• 10% overage = 873 ×1.10 = 960.3 sq ft
• 15% overage = 873 × 1.15 = 1,003.95 sq ft
• Final range: 960 – 1,004 sq ft

Tip: Over-ordering is better than running short. You’ll thank yourself.

Step 6: Think About Orientation and Style

Your layout affects your material needs more than you might expect. The orientation and pattern you choose—whether horizontal, vertical, or diagonal—can impact how much siding you’ll need. Horizontal layouts tend to be the most efficient, often allowing for longer board runs with minimal cuts. Vertical installations, like board and batten, may require more precise trimming and additional material for battens or edge alignment. Diagonal or herringbone patterns create more waste due to angled cuts and less efficient board usage, so they often demand a higher overage. Before ordering, decide on your installation style so you can plan accordingly and avoid surprises once the boards arrive.

• Horizontal siding uses longer boards and is the most common
• Vertical (board and batten) may require extra trim
• Diagonal or herringbone patterns waste more—add up to 20%
• Decide on your installation pattern before you order—it changes how much material you need.

Tip: Share orientation details with our customer service team. We have many years in the business and can help ensure that your wood order will meet your requirements.

Step 7: Finalize and Order

Now plug your measurements into our Reclaimed Wood Wall Siding and Paneling Square Foot Calculator with Inches to get an accurate estimate of the square feet that you’ll need. Our team can translate square feet totals into linear board feet depending on the reclaimed wood products that you want to purchase.

If you want to make this calculation yourself, you can take the square feet totals and use our Square Feet to Linear Feet Calculator. This tool allows you to input your measurements into a room square foot calculator with inches along with the board widths for the siding product you are interested in, and it will calculate the linear feet that you need for the project.

Reminder

This is a measuring guide, not an installation guide

What Is a Rain Screen—and Why Does It Matter?

When installing exterior siding, especially wood siding, it’s critical to create a way for moisture to escape. That’s where a rain screen comes in.

A rain screen is a system that creates a ventilated gap between the siding and the wall sheathing. It’s typically made up of vertical furring strips or a drainage mat that lifts the siding slightly off the wall surface. This gap allows air to circulate and water to drain, preventing moisture from getting trapped behind the boards.

Without a rain screen, moisture that gets behind the siding—whether from rain, condensation, or capillary action—can build up and lead to mold, rot, or premature material failure. This is especially important with reclaimed wood, which can be more sensitive to prolonged exposure if not properly ventilated.

Rain screens don’t affect your siding measurements because they only change what’s behind the siding, not the surface area being covered. But they do dramatically improve the durability and long-term performance of your installation. For best results, follow best practices from the North American Architectural Woodwork Standards (NAAWS) or consult with your contractor to ensure the rain screen is properly integrated into your siding design.

Ready to Get Started?

Measuring your home for reclaimed wood siding doesn’t have to be complicated—just follow a few key steps:

• Calculate the total square footage of your exterior walls
• Subtract the area of large windows and doors
• Add 10–15% extra to account for trimming, cutting, and layout flexibility

By carefully planning and measuring, you’ll ensure your siding project runs smoothly from start to finish. Whether you’re a homeowner or working with a contractor, double-checking your numbers helps avoid costly delays or last-minute orders.

For best results, we strongly recommend following the North American Architectural Woodwork Standards (NAAWS) Guidelines for Siding Installation to ensure proper handling and placement of your reclaimed wood materials.

To make planning even easier, be sure to explore our other tools:

• Reclaimed Wood Flooring Square Foot Calculator
• Square Feet to Linear Feet Calculator
• Linear Feet to Square Feet Calculator
  

Have questions or need help with your estimate? Reach out to E&K—we’re here to help bring your vision to life with one-of-a-kind reclaimed wood siding that adds beauty, warmth, and history to your space.