How to Quickly Measure a Window for Replacement
To get an accurate measurement of your window, measure from the outside of your home or building. Get the width first and then the height.
We’ll show you exactly how in this quick guide.
Key takeaways
Measure from the outside of your home or building.
Measure the opening where the window is fitted– not the frame. Imagine the hole in the wall that is left if you were to remove all the components of your window. That’s what you want to measure.
Hold the tape measure straight and firm. A slight slack or diagonal offset can make your measurement inaccurate.
Take readings in millimetres as this is the standard that window manufacturers use in the UK.
What you’ll find here:
How to Accurately Measure the Width of Your Window
1. To get an accurate width measurement, measure from brick to brick: top, middle, and bottom. Windows are never 100% straight so it’s best to get a measurement from three spots.
2. Get the smallest number and subtract 10mm or 1cm from it. That’s the width of your window.
How to Accurately Measure the Height of Your Window
1. To get the height of your window, measure the brickwork opening: left, right, and centre.
2. Get the smallest number and subtract 10mm or 1cm from it to find your window’s height.
Get diagonal measurements
Measure your window diagonally from top left to bottom right and top right to bottom left. This will help you determine if your window is square.
If your measurements turn out different, your window opening might be misaligned. This can cause problems during installation. Be sure to consult a professional window installer before placing an order.
The 10mm/1cm Rule for Fitting Double Glazed Windows
If you’re installing double glazed windows, take away 10mm or 1cm from the smallest measurements of your window width and height. You will need this allowance to fit your new window without the need for spacers.
Tips for Window Measurement
- ✔ If you would like to install the windows yourself, check in with your manufacturer to see if they have specific guidelines to ensure an accurate fit.
- ✔ Metal tape measures work, but a fabric tape measure eliminates the worries of scratching the glass panes.
- ✔ Measure at least twice.
Conclusion
If you are in any doubt about your measurements, don’t hesitate to contact a professional installer. Any installation fee will offset the money you’ll burn if you end up purchasing the wrong sized window.
If you have already taken your measurements and would like to move to the next steps, we can help in two ways.
First, you can use our free price comparison tool to compare quotes from different UK manufacturers and installers. Our comparison tool has helped homeowners get the most cost-effective quotes.
Second, you may reach out to us so we can request quotes on your behalf. We are extending this as a free service. Absolutely no commitment.
One more thing: if you’re installing double glazed windows for the first time, there might be grants available in your area.
Please visit our guide to double glazing grants to see if you qualify.
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