Internal Bifold Door Size Guide & How To Measure For Them Correctly

Looking to purchase internal bifold doors but unsure what size you need? Our guide details the standard sizes available and includes information on how to shop internal bifolds for your home. You will also find information on how to measure bifold doors so you always get the correct fit for your doorway. And if you have any further questions after reading just get in touch and we’ll be happy to help.

Internal Bifold Door Sizes

Internal bifold doors have a standard height of around 2047mm, or 6ft , but you should always double-check the height of your opening. You’ll find measurement guidance further down the article.

The width of internal bifold doors varies considerably, and sizes also differ by the number of panels you wish to feature in your door. Similarly panels differ in sizes too, bifold door panels range between 400mm and 900mm. Standard internal bifold door width sizes usually start around the 1200mm or 4ft mark but we have sizes raging up to 15ft. Width sizes will depend on the manufacturer and how extensive their range is. Below is a size chart to offer further guidance on the sizes and panels we have in our range.

Internal Bifold Door Size Guide

No. of PanelsFrame Width (mm)
Three Panels1218 
Four Panels1601 
Five Panels2943 
Six Panels3740 

The doors described here come in a range of different configurations. There are standard bifold doors, which consist of a single stream of panels which unfold from one side of the frame; there are ‘French-fold’ doors which consist of two equal groups of panels which extend from either side of the frame and meet in the middle; and there are ‘traffic-door’ equipped bi-folds, which come with a single door on one side to allow for easy passage.

When measuring for bifold doors, precision is key. A difference of just a couple of millimetres can be significant when it comes to excluding drafts and ensuring the smooth operation of the door.

What Size Internal Bifold Door Do I Need?

Assuming you’re not bringing in any help to measure your doors for you, you’ll need to break out the tape measure before placing your order. If you’re going to be tearing out the old frame and installing a new one, then you’ll need to figure out the width of the aperture; if you’re installing a new bifold into an existing frame, then it’s the interior dimensions you need to worry about.

How To Measure For Internal Bifold Doors

1. Check The Door Alignment

Before we measure, we should ensure that the door is square and true. This means taking a spirit level and placing it against the edges of the opening.

2. Measuring Up

To check your bifold door frame size, you’re going to be taking a total of six measurements. Three vertical measurements, on the left, right and centre; and three horizontal measurements, along the top, middle and bottom. In both cases, the three measurements should be within ten millimetres of one another. The smaller the difference, the better. If you’ve got a serious discrepancy, then you’ll likely have to adjust the frame before you get the door installed (though this is less of a problem if a new frame is going to be installed). In both the horizontal and the vertical cases, you’ll want to use the smallest measurement. Subtract ten millimetres’ clearance, and you have the length of your door

3. Sunken or Flush?

Once you know what size you’re going for, you can think about whether you’d like a sunken track, which is placed beneath the floor level, and a flush one, which is placed at floor level. Obviously, having the track higher will mean that your door needs to be moved up out of the way

4. Panel Sizes

The panels that go into bifold doors come in various sizes. For the most part, you’ll have a choice between a large number of narrow panels and a small number of wide ones. This enormously influences the look of the door and affects the amount of light that can pass from one side to the other. But it also has practical implications. Wider panels will need more space to open out into, meaning that you’ll need to clear room on one side of the door. But narrower ones will take up more space on one side of the door when it’s open.

My Bifold Doors Don’t Fit. What Shall I Do?

If you’ve measured carefully, then the chance of a mismatch between the size of your door and the size of the opening will be minimal. Check that your doors fit the opening as soon as they arrive – if there’s a problem, the best course of action is almost always to send them back. This is time-consuming, but it’ll save you from having to mess around with saws and sandpaper to get the problem corrected.

Altering Internal Bifold Doors

Now, any changes you make to your door will be permanent. Make just one wrong move, and you’ll throw away the cost of your door! It’s therefore first exploring other ways of addressing the problem. For example, if you find that your door is catching on the floor as it opens, it might point to a problem with alignment rather than the size of the door itself. It’s much easier to move the pins and rails around than it is to start making changes to the panels themselves.

With that in mind, you might have already explored these options and decided that you absolutely must shrink your doors slightly. This is tricky because most bifold panels are of the ‘composite’ sort. They’re made from high-quality wood surrounding a stronger, less attractive ‘core’. If you sand all the way into the core, the results can be unsightly. Each panel comes with just a few millimetres of ‘lipping’ around the edges, and so you’ll need to be very careful.

For this reason alone, you’ll want to take a little bit off both edges of every door, rather than a lot off one. That’s before we even think about how strange it might look to have one panel slightly smaller than all of the others!

How To Cut Internal Bifold Doors To Fit

To get this right, you’ll want to remove the entire door assembly. Do this by loosening the pivot at the bottom until there’s enough slack to lift the entire door from the frame. Then remove the hardware and lay the panels flat.

Next, we need to do a little bit of basic maths. You need to find the difference between the current width of the entire door and the ideal width. This is the amount of timber you need to trim. You need to then divide this figure by the number of panels in the door, and by two (the number of vertical edges each panel comes with). This figure, which should ideally be in the low millimetres range, needs to be removed from each edge of each door in the set.

We’re almost ready to start trimming our bifold doors to fit. But before you start cutting, you’ll need to very carefully measure and draw the new edges with a pencil onto both sides of the door. Use masking tape to clearly mark your edges, and score along the line with a Stanley knife. You’ll then be able to saw along the edge, leaving a little bit of space so that you can sand the edge smooth after you’re done. In some cases, you might not even need to use a saw.