How to measure windows: uPVC Windows Measuring Guide

19 May 2021

A lot of people ask how to measure windows. It’s a question that many people struggle with, so we’ve created this guide for you! If you’re thinking about buying replacement uPVC windows, then it is important that you know how to measure the size of the window required. This article will show you how to do just that and more!

To start with, avoid the temptation to measure only the existing frame. Instead of measuring the window frame, you need to measure from the brickwork. Otherwise, you’ll end up with inaccurate measurements and your new window will not fit properly.

It’s also worth noting that some window companies will not simply be able to take your measurements and provide a perfectly fitting window. Different companies factor in different allowances, and some don’t factor any in at all, so it’s always advised to have the company you choose for your window installation to do their own measurements. The information below is designed to give you a rough guide to getting an accurate measurement, so that you can obtain costs for your new windows.

With the technical bits out of the way, let’s look at measuring for your replacement windows.

How to measure for new uPVC windows

Measure window width

Measure the width of your window by using a tape measure or ruler. The measurement should be taken from outside to outside. You will also need to take into account any overhanging eaves (most likely on the front façade), as these will reduce the size of what can fit inside the opening.

Measure window height

Next up is height – measuring how high your current window is in cm’s or inches. It doesn’t matter if it’s an internal or external frame; just make sure that they are both measured with your tape measure/ruler!

Again, measure from the brickwork opening.

Measuring window openings

To measure the window openings, simply measure the width of the opening at the top, middle, and bottom.

Now you will need to identify the narrowest measurement and deduct 10mm off of that. This figure then provides the width.

Next, to get the height, measure the height of the opening at the left, middle, and right. Same as before, take the shortest measurement, deduct 10mm, and that will give you your height.

These steps will need to be repeated for each window opening.

Sounding a little complicated?

Getting the measurements for your replacement windows right is a crucial step. The last thing you want is to have spent hundreds on a new window, for it to not fit.

To help you out, take a look at our standard window sizes guide, which will provide some guides on how small or large windows generally are.

We always recommend having a professional window fitter measure up for your new windows before placing an order – just to be on the safe side. But if you still want an idea of the cost, our online window designer will allow you to enter in the exact sizes, rough sizes, or use our predefined window sizes, to get an idea of the cost.

After you have obtained a window quote, and considered if you’re happy with the guide price, you could then ask for a window fitter to come out and formalise the quote to give you a final figure, ensuring you get everything just right.