How to Measure Windows for Replacement

Welcome to our guide on measuring windows for replacement! If you’re planning on upgrading or replacing your windows, it’s important to get accurate measurements to ensure a proper fit and optimal performance. In this article, we will take you through the 12 steps necessary to measure your windows correctly, as well as some helpful tips and tricks along the way.

Measuring Windows for Replacement: Step by Step Guide

Step 1: Prepare the Tools You Will Need

Before you start measuring, gather all the necessary tools. You will need a measuring tape, pencil, paper, and a calculator. It’s also helpful to have a level, a straightedge, and a ladder if you need to measure windows on higher floors.

Step 2: Determine the Type of Window You Have

Identify what type of window you have: single-hung, double-hung, casement, sliding, or picture. Each type may have slightly different measurement requirements, so it’s important to know what you’re dealing with before you start.

Step 3: Measure the Width of the Window Opening

Start by measuring the width of the window opening. Measure from the inside of the window frame at the top, middle, and bottom, and record the smallest measurement. Write down the measurement in inches.

Step 4: Measure the Height of the Window Opening

Measure the height of the window opening in the same way as the width. Measure from the inside of the window frame at the left, center, and right, and record the smallest measurement. Write down the measurement in inches.

Step 5: Measure the Depth of the Window Frame

Measure the depth of the window frame by measuring from the interior trim to the exterior trim. Record the measurement in inches.

Step 6: Check for Squareness

Check if the window opening is square. You can do this by measuring diagonally from corner to corner. The two measurements should be the same. If they’re not, take note of the difference, and make sure to order your replacement windows accordingly.

Step 7: Measure the Glass

Measure the glass dimensions of the existing window. Start with the width, from top to bottom. Then, measure the height, from left to right. Record the measurements in inches.

Step 8: Measure the Sill Angle

Measure the sill angle if you’re replacing a casement or awning window. Use a level to find the angle of the sill, and record the measurement in degrees.

Step 9: Measure the Jamb Width

Determine the jamb width by measuring the side of the window frame from left to right. This measurement is important if you’re replacing a double-hung or sliding window, as it will affect how the replacement window operates.

Step 10: Determine the Window Operation

Identify the window operation by checking if it slides up and down, swings in and out, or doesn’t move at all. This information will determine what type of replacement window you need.

Step 11: Take Note of Additional Details

Take note of any additional details about your window, such as the material, color, and hardware type. This information will be helpful if you plan on ordering a replacement window that matches the existing one.

Step 12: Double-Check Your Measurements

Before ordering your replacement window, double-check your measurements to ensure they’re accurate. It’s better to take a little extra time to be sure than to end up with a replacement window that doesn’t fit properly.

Tips and Tricks for Measuring Windows

1. Measure from the Inside

Always measure from the inside of the window frame. This is because the exterior trim may vary in thickness, which can affect your measurements.

2. Use a Measuring Tape

Don’t try to estimate measurements with a ruler or yardstick. Use a measuring tape to get precise measurements.

3. Measure Twice

It’s always a good idea to measure twice to ensure accuracy. If your measurements don’t match, measure again until you get consistent results.

4. Consider Energy Efficiency

When choosing replacement windows, consider energy efficiency. Look for windows with energy-efficient glass and frames that will help reduce energy consumption and lower your energy bills.

5. Don’t Forget to Check for Building Codes

Make sure to check your local building codes before ordering replacement windows. Some areas have restrictions on the types of windows you can install.

6. Take the Time to Shop Around

Don’t settle for the first replacement window you find. Take the time to shop around and compare prices, styles, and features to find the best window for your needs and budget.

7. Consider Professional Installation

If you’re not familiar with window installation, consider hiring a professional to install your replacement windows. This will ensure proper installation and optimal performance.

8. Get Help if You Need It

If you’re not sure about any of the measurements, or if you’re having trouble with the process, don’t be afraid to ask for help. A knowledgeable salesperson or contractor can help answer your questions and guide you through the process.

9. Keep Your Measurements Handy

Once you have your measurements, keep them handy. You may need them again in the future, and having them readily available will save you time and hassle.

10. Take Care of Your Replacement Windows

Properly maintaining your replacement windows will help them last longer and perform better. Follow the manufacturer’s instructions for cleaning and maintenance, and have them serviced regularly to ensure optimal performance.

That’s all for our guide on measuring windows for replacement. We hope you found it helpful! Remember, taking accurate measurements is an important step in ensuring a proper fit and optimal performance for your replacement windows.

Advantages and Disadvantages of How to Measure Windows to Replace


1. Precise measurement – By measuring your windows accurately, you can be sure that you will get the right size windows and prevent any gaps or leakages.

2. Cost-effective – Proper measurements can help you order the correct size of windows, which can save you the cost of resizing or getting new ones.

3. Increased energy efficiency – Measuring your windows before replacing them will ensure that you get custom windows that fit tightly, reducing energy loss and saving on your energy bill.

4. Better aesthetics – Custom fitting windows improve the overall appearance and value of your home, enhancing the curb appeal.

5. DIY opportunity – Measuring your windows can be done by yourself, providing an opportunity for DIY enthusiasts to enhance their skills and save some money on installation costs.

6. Increased safety – Measuring your windows before replacing them can prevent any accidents or mishaps that may occur during installation.

7. Time-efficient – By measuring your windows properly, you can save time and frustration by avoiding having to return or exchange windows that were improperly sized.

8. Increased customer satisfaction – Proper measurement and installation of windows can increase the satisfaction of homeowners with the outcome of their window replacement project.

9. Easy maintenance – Custom fit windows are easier to clean and maintain because they are designed to fit perfectly without gaps or obstructions.

10. Customization – Measuring your windows allows you to customize your new windows to your exact preferences, ensuring that you get the perfect fit and design that you desire.


1. Complexity – Measuring windows involves some level of complexity, which may discourage non-professionals from performing this task.

2. Time-consuming – Measuring windows takes time, and it requires a considerable amount of patience and attention to detail.

3. Risk of error – Incorrect measurements will result in improperly sized windows, which can lead to gaps, leakages, and energy loss.

4. Limited equipment availability – Homeowners may not have all the necessary equipment required to measure windows accurately, which can limit their ability to measure the windows themselves.

5. Limited design options – Custom fitting windows are limited to the available designs, which may limit homeowners’ ability to get the exact design they want.

6. Increased costs – Measuring windows accurately may require the installation of additional hardware or devices that can add to the cost of the replacement project.

7. Dependence on professionals – Homeowners who lack expertise and tools for measuring windows must rely on professionals to complete the job accurately.

8. Improper installation – Even with accurate measurements, improper installation can result in gaps and leakages that can compromise the energy efficiency of the windows.

9. Weather restrictions – Measuring windows accurately requires favorable weather conditions, which can limit the time and season of installation.

10. Prolonged installation time – Custom fit windows may require a longer installation time than standard windows, which can prolong your window replacement project.


1. Why do I need to measure my windows?

You need to measure your windows to ensure that the new window you purchase will fit perfectly in the opening. Measuring your windows can also help you determine the type and size of window you need to replace it with.

2. What tools do I need to measure my windows?

You will need a measuring tape, a pen, and paper to write down the measurements.

3. How do I measure the width of my window?

Measure the width of the window from left to right at three different points – the top, middle, and bottom. Use the smallest measurement as your width.

4. How do I measure the height of my window?

Measure the height of the window from top to bottom at three different points – the left side, middle, and right side. Use the smallest measurement as your height.

5. What should I do if my window is not a standard size?

If your window is not a standard size, you will need to custom order a window to fit the opening. Contact a window manufacturer or supplier for help with this.

6. What units of measurement should I use?

Use inches to measure your windows.

7. Do I need to measure the entire window frame?

No, just measure the opening where the window is located.

8. Should I measure the interior or exterior of the window?

You should measure the interior of the window opening.

9. What if I’m not sure if I measured correctly?

It is always a good idea to double-check your measurements. You can also contact a window professional to help you with measuring.

10. How do I measure for replacement windows if I don’t have the old ones installed?

You will need to measure the rough opening where the windows will be installed. The rough opening is the framed opening in the wall where the window will go.

11. How do I measure for replacement windows in a brick or masonry opening?

You will need to measure the inside opening of the brick or masonry with a measuring tape.

12. Can I install replacement windows myself?

Yes, you can install replacement windows yourself. However, if you are not comfortable with doing it yourself, it is best to hire a professional installer.

13. How long does it usually take to replace a window?

The time it takes to replace a window varies depending on the size and type of window, as well as the skill and experience of the installer. Typically, it can take anywhere from a few hours to a full day to replace a window.

How to Measure Windows to Replace

If you’re in the market for new windows, one of the first things you need to do is measure your current windows. This will ensure that your new windows fit perfectly and function properly. Here’s how to measure windows to replace.


Measuring your windows may seem daunting at first, but it’s really quite simple. By following these steps, you can be sure that your new windows will fit properly and provide optimal performance. Remember to measure both the height and width, and to take multiple measurements to ensure accuracy. And if all else fails, consult with a professional to ensure that you get the perfect fit for your replacement windows.


Thank you for reading our guide on how to measure windows to replace. We hope that you found this information helpful and informative. If you have any questions or comments, feel free to leave them below. And if you’re in need of replacement windows, be sure to measure carefully and choose quality products to ensure that you get the best possible results.

Until next time, happy measuring!