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How to Measure Window Glass for Replacement

Shane's Glass • Jan 13, 2023

Are you planning to replace your old window glass with a new one? You might need an expert in glass repairs that can assist you with your window glass replacement needs. But before that, it's important to learn first how to measure windows accurately.


A common issue brought on by an old glass window frame is a leaky window. Caulk can be used to fill in the cracks and crevices, but it may not always be effective, especially if the window glass is already completely damaged and needs to be replaced. Thus, not fixing it immediately could even cost you more than you expect.

Replacement Glass for window sill
Replace old windows

The best cost-effective solution is to replace any old glass or damaged window frame as quickly as possible if you want to skip all the inconvenience and repair costs. As a matter of fact, you can also save money in the long run on your energy bills.

What is a Replacement Window?

Replacement windows are designed to fit into your window's existing rough opening, which saves the contractor from having to take down the outer components of your house in order to install new windows.

Replacement windows
replacement of broken windows

Replacement windows are one of the best upgrades that you can get since they have the potential to increase your home's value. However, without proper installation, they won't work effectively with your house's air and water leaks.

This is the reason why you should invest with a reliable glass services company to ensure that you get to maximise your windows' functions for a long period of time.

replacement of broken windows
Window rough opening

Rough Opening and Size of the Window

The area where the window frame is placed is known as the rough opening. When selecting a frame size, it is important that you get the right opening dimensions. However, since you will also have to consider the placing of the window sill, window headers, and window trimmers, you should allot a space allowance for them. Hence, the size of the replacement glass window should be smaller than that of the rough opening.

Importance of Getting the Right Measurement for Your Window Frames

Windows are essential in turning a house into a home. Glass windows, in particular, allow homeowners to enjoy lovely panoramic views of their property and its surrounding areas while providing additional light and ventilation to their home. Indeed, windows have the power to influence a home's look, atmosphere, and interior design.

Replacement windows
Prevent leaks

But most importantly, they are essential in keeping water from leaking out of your home while ensuring that there is proper airflow inside it.

Thus, it is important that your windows fit perfectly so as to avoid any issues that may interfere in the future.


Ensure that you get precise window measurements when replacing your old glass window frame with a new one. Otherwise, it won't fit the hole.



Simply measuring across the hole won't work since the space where the glass must fit is bigger than the hole you can see.

New replacement windows
Measure windows accurately

Steps on How to get Accurate Measurements for Your Window Frame

No need to use a special equipment to measure your windows. By using a measuring tape, you can measure your windows accurately like a pro. Follow the steps below to precisely estimate the size you need for your replacement windows.

Step 1: Remove Your Old Glass

You might need to take the old glass out of your windows first before you can accurately measure them.


To prevent breaking, attach a masking tape in an interlaced pattern on both sides of the glass and use gloves for additional safety and protection. If the glass is already cracked or broken, carefully take out each piece and carefully remove the frame.

old window frame

Removing your old glass means that you have to remove the entire frame including the window jambs and everything that holds it. Since this can be complicated and sensitive to do, you may want to skip this part and just call a professional to do the work for you.

Measuring tape

Step 2: Measure Glass Horizontally

Once the old glass has been removed, you can now start measuring around the window frame. Always make it a point to measure three points at different ends.


The first step is to measure the length of your window glass horizontally. Start at the top then go to the middle down to the lowest point (bottom part). Do this carefully to ensure that you get an accurate indication of whether the window has equal spacing or not.

It is important to note that obtaining the right thickness for your window is essential in ensuring that the window's placing is durable and sturdy. A thick window also needs a wider rough opening.


Now that you have obtained three dimensions, use the smallest measurement to get your final width.

Width measurement
New windows

Step 3: Measure Glass Vertically

After you have measured your glass windows horizontally, you may also need to do the same but on a vertical angle to measure your glass window's height.



Take the vertical dimensions by measuring from the window sills to the head window jambs on the left side, the centre, and the right side of the window. Similar to your width, take the height's smallest measurement before deciding to buy your replacement window.

Step 4: Measure Glass Diagonally

If you want to ensure that you really get accurate measurements, you can also measure your windows diagonally on both sides. Even though this is merely an optional step, doing this won't hurt your time and effort since it is quick and easy to do.

Measuring tape
one jamb

Step 5: Measure the Depth of Your Glass

Not all windows are the same and not all will fit the depth of the window's rough opening. Hence, it is important that you measure the distance between the window frame's edges by running a tape measure from the outside to the inside of the frame.



Do this in several points so you can assure that you are getting the exact depth measurement for your glass replacement.

Getting Final Measurements

Inch is the most common standard of measurement that you can use to measure your windows. But if you have better ways to measure them effectively, you may opt to measure them using other methods.



Always get the smallest measurements of your window's length, width, and height when getting your final measurements. This is because you always need to consider the other components that make up the entire window frame.

Measuring dimensions with
Replacement glass

What is the Standard Size for a Window Frame?

When getting window measurements, most people look for the standard size not only because it's easier to do but because it is also actually less expensive.

A standard-sized window frame and window jamb are designed to fit most window holes. Single hung windows and double window frames typically have a standard width measurement of 25 to 48 inches. For casement windows, they can vary from 12 to 36 inches. While large designs such as picture window, bow window, and bay window can possibly range from 90 to 130 inches.

Bay windows
Replacement glass

Most window rough openings range can accommodate these window sizes. However, it is always the best to measure your windows first before placing an order.



If a ready-made window is not available, you must look for a good glass replacement company so you can choose the perfect custom-cut glass alternative for your needs.

How Much Will a Window Replacement Glass Cost?

The cost of replacing windows typically ranges between $300 to $1,200 with an average cost of $600. However, prices may still vary and possibly go up higher depending on the size, style, type of material used, and if there are additional labor costs incurred.

Costs for window materials can range from $80 to $1,300 depending on its durability and modification properties.



Replacement windows services

Reliable Glass Window Replacement Services in Canberra

If you are looking for the best glass window replacement services in your area, Shane's Glass is your one-stop solution for all types of glass needs.



Shane's Glass specialises in high quality glass replacements, repairs, and installation in Canberra. With over 45 years of experience in the business, we can provide you with the most precise measurements for your windows at a reasonable price. Contact us today for a free quote of our services.

  • GET IN TOUCH

    I hope you enjoy reading this blog post.

    If you’d like more information or a free quote on any one of our services, simply get in touch today.


    We’re always delighted to assist.


    GET IN TOUCH

I hope you enjoy reading this blog post.

If you’d like more information or a free quote on any one of our services, simply get in touch today.

We’re always delighted to assist.

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