
Each and every aluminium bifold door is unique – each with a wide range of different openings, accessories and colours avaliable. Whether your opting for internal doors or new bifold doors for your outdoor patio, it’s crucial you know how to measure bifold door openings correctly. There are many different external and internal bifold door sizes available, but without the perfect fit, your new door panels may not operate smoothly.
In this blog post, we will explore the simple steps to take an accurate measurement to get the right fit for your door opening.
So, let’s dive in and help show you how to measure the opening for your brand new bifold door panels!
Before taking the three height measurements, you should ensure the aperture for the new doors is flat, level, straight and plumb at every side. There should also be a solid structure to fix the door frame to ensure the door panel is secure. If you are unsure on your gap, you should ask advice from a professional, as a rough opening may give an improper measurement for the external doors.
Remember accuracy is key, so ensure each measure is precise to avoid any costly mistakes when measuring for your bifolding door. You should take accurate measurements according to the structural openings where you would like your new doors to go. You should check with your supplier on their fitting tolerance and maximum or minimum door height.
Precisely record the three measurements: length, width and a diagonal measurement. The smallest height and width measurement will determine the overall frame manufacturing size.
Bifold doors require clearance space for smooth operation. As well as the aperture size, you should measure the depth of the space available for the doors to fold back when open. Ensure there’s enough clearance to accommodate the full width of the doors without obstruction.
You should think about how much space will be needed either side of the door set when opening and closing the doors. This should be measured in your internal room or external space, depending on if you are installing open out or open in doors.
Use a level to check if the door opening is square. Accurately measure diagonally from one corner to the opposite corner and then from the other corners. If they are equal, the opening is square. If not, adjustments may be needed to ensure proper alignment and enough space for the doors.
Before finalising your order, double-check your measuring to ensure accuracy. Spend a little extra time verifying each measurement to avoid dealing with the aftermath of ordering the wrong door sizes. Once you have checked these over, you should be able to determine the correct size for your new doors. Every manufacturer will also have a fitting tolerance, giving you a little wiggle room for an incorrect taking, so do check with these prior to ordering.
If you’re unsure about any aspect of the measuring process, you should contact a professional to assist. We do offer a measuring and installation guide to assist you in the process, but we do suggest your doors are installed by an experienced professional. If you have any questions, please ensure you contact our team at UK Doors Online on 01924 929 600. We can offer advice and help ensure your bifold doors are measured and installed correctly.
Each house is different, but you may also find that your opening is of a standard height and width, meaning you may be able to opt for one of our standard sizes. These doors are also ideal for extensions or garden rooms, as you can customise your build around the standard size. Plus, you’ll be able to precisely measure for these new doors. We have many standard sizes available to suit both a larger and smaller opening, so check out our online shop today!
By following these top tips for measuring your bifold doors, you can ensure a smooth and successful installation process, resulting in doors that fit perfectly and function flawlessly for years to come. So, grab your tape measure and get started on transforming your space with stylish and functional bifold doors!

Here are some of our final top tips for you to take away when measuring for your new bifold doors!
Also read our other helpful tips, including how to toe and heel your bifold door and how do bifold doors lock?
Do you have any questions or need further assistance? Our team of experts are happy to help – just contact us at sales@ukdoorsonline.co.uk or give one of our friendly sales members a call on 01924 929 600.
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I have recently bought 3 pane bi-fold doors and replacement glass for my previous doors. The door fitters I used praised the quality of the doors for many reasons. I would like the thank the customer service I received through the quotation, ordering and delivery process. I would recommend UKDoors online to anyone in the future.
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One of the best customer care experiences I’ve ever had- nothing is too much trouble, went above and beyond, and super friendly, speedy communication. The price of the doors was also excellent. Thank you to the whole team!
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4 panel bifold doors ordered and delivered in the 3 week stated timeframe and prove to be well fitted, elegant and robust with a fine finish. Would definitely recommend.
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We deal with UK doors online, at least once a month, for the last 3 years or so. From the staff on phone to the guys doing the deliveries the service is great. Any issues are resolved in a great timely manner. 100% wouldn’t go anywhere else for our bifolds, windows and composite doors.
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This is our first time using ukdoorsonline and I must say that it has been a pleasure, very easy ordering and the whole process from order to delivery was like clockwork as a small business the service we got from this company was exceptional. 100% will be using them again and again, thank you all at ukdoorsonline.
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A+++ quality product, great value and excellent customer service. Had an excellent experience purchasing bifold doors and window with integrated blinds from UK Doors Online. Dealt with Paul who was lovely – friendly, helpful and knowledgeable. I’m delighted with my new doors and window. Will definitely use UK Doors Online again.
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