How To Measure For Replacement Windows

Updated:  September 27, 2019

Replacement windows:  Your little Sidney Crosby wannabe shot a hockey puck just shy of the driveway net and suddenly you need a new front window.

You just bought a new house, but the windows are old, drafty and not energy efficient.

You’re doing a big home renovation and changing up the exterior to increase curb appeal and value.

Whatever your reason for replacement windows, the decision has been made and now it’s time to get an estimate. The first place to start is by measuring the current windows. Some people will measure on their own first to get a rough idea of size, but many head straight to the professionals.

Let’s take a look at the steps to measuring and then dive into the importance of measurement accuracy before you move forward with replacement windows.

Four Steps To Measuring For Replacement Windows

  1. Gather up the necessary tools! You’ll need a measuring tape, ladder, pencil, paper and side ruler.
  2. Take three horizontal measurements of the window frame for the rough opening width. Measure at the top, middle and bottom to be sure.
  3. Take three vertical measurements of the window frame for the rough opening height. This time, measure at the left, centre and right to be sure.
  4. Now measure the depth of the window’s opening.


It’s also helpful to draw a picture of each window and note the measurements on it. This will help with visualizing when you are ready to start looking for estimates from window suppliers.

Importance Of Accurate Window Measurements


This is not the time to do a ‘ballpark’ measurement for your replacement windows! The accuracy of a window measurement is critical to how well your window will function. So if you’re short on time, lacking the tools, or just want to be sure you get the most accurate measurement possible the first time, call in a professional window installer and forget the four steps all together. Here are a few reasons why accuracy matters with replacement windows.

First, when a measurement is not precise there will be drafts. If the measurement was even slightly off, there will be too much space around the window which will result in gaps around the outside. Those gaps will cause precious hot or cold air to escape, and moisture to come in.

Drafts are also caused when windows warp and the seals between the panes break. This occurs when replacement windows are crammed into too tight of a space and they expand and contract against the surrounding material.

Secondly, accuracy is important for the stability of the window. Due to the expansion and contraction of the window in varying temperatures, there needs to be some space between the glass and the frame. Too much or too little space can affect the stability of the window.

Last but not least, consider the exterior space you have to work with if you want to opt for a swinging window—such as a casement or awning window. Measuring the exterior clearance to swing the window in the desired direction is essential.

Know When To Call In The Professionals For Your Replacement Windows


If in doubt, or if you’re ready to get your replacement windows installed, it’s always a good idea to work with a professional window installation company. Even the slightest inaccuracy in measuring could result in an installation disaster and wasted money. Plus, when you work with a professional, you’ll save time in the process and benefit from a window warranty when a licensed professional handles all aspects of the process. Start your replacement windows today by contacting us for a quote


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Weaver has over two decades of experience and provides comprehensive installation services for windows, doors, and aluminum in the Barrie region, making it a convenient option for all project sizes.