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How To Measure A Door Guide




A very handy guide indeed

We, at The Posh Door Company, love helping our customers as much as we possibly can, which is why, we have created this guide, especially for you.

You may be very surprised to learn that doors come in a wide range of different sizes and these include “industry standard” sizes which most suppliers will use. However, we know that not every house is the same and that you will need a totally different door size when compared to someone else’s home. 

Most suppliers will tend to stick with the “industry standard” sizes but we, at the Posh Door Company are more than happy to say that we can cater for most homes, with very strange sizes indeed!

We can provide you with outstanding bespoke doors that have been made to measure and will fit whatever space you have, perfectly!

When you first begin the process of finding a new door it’s extremely important to know that the starting point is to measure the opening that you have to fill. This is the place that your current door fits into. 

The majority of our doors, here at The Posh Door Company can be trimmed or planed down so that they will suit whatever opening size you have. However, its’s important to note that the threshold for altering your doors will be different with each manufacturer.

When you start thinking about what size door you’re going to need it’s important to note that there will need to be a 2-3mm gap around your door. This allows you to open and close your new doors. This gap also ensures that there won’t be any cracks or warping, during the colder months. Your doors are more prone to a little bit of swelling, at this time of the year, due to humidity changes.

Measure the opening you have, to be as accurate as you possibly can be, especially if you are buying a few different doors for your home. The openings for each door will sometimes be very different indeed, due to them being in different locations in the home and of course, the way your home was built.

The door measuring process

First of all, you’re going to need a tape measure to carry out the door measurements. Alternatively, if you have a laser measure, then that would be another excellent tool to use. 

If you don’t have a tape measure or a laser then don’t worry, maybe your smartphone will do. There are many apps out there including Tape Measure and Easy Measure, which you can get from the Apple App store. Or, if you have an Android phone use Google Measure or AR Ruler App. 


You can find the width of your door by running a tape measure along one side of the door going from left to right. Make sure that you are only including the door and no other part. Write down this number.

Do the same again but at another point on the door. This is because some older doors aren’t rectangular and so you need to take a few measurements. Use the biggest number you measure as the width of your door.


Now, run the tape measure from the top of the door to the bottom, going in a straight line. Double check, as you go along that you are not including any other door part, for instance, a door sweep. Once again, make a note of this number.

Like we said when measuring the width, your door might not be perfectly rectangular and so you’ll need to take a few measurements, going from top to bottom at different points on your door. Then, take the largest number as your door height.



To get the thickness you have to run the tape measure from the edge of one side to the edge of another. Make a note of this number. Then you have to measure the door jamb on the frame. This checks that they’re a similar size.

Can I measure the door I’m going to be replacing?

Yes, most definitely you can. If you already have a door hanging then it would be far easier to measure that door, rather than measuring the opening. First of all though, check the door, to see if it’s snug in the frame and there are no problems with rubbing on the frame or if there are any gaps around the edges. If, however, you’re not happy with the fit of your old door or if you are going to change the door frames then we recommend measuring the opening in the wall. 

Measuring the opening

If you don’t already have a door hanging then you will have to measure the opening in the wall. If it’s a new opening then there may not be a frame there yet. When you come to measure an opening without a frame, it’s known as brick to brick opening. If you do have a frame there, this is known as frame to frame. Once you have your measurements , you will be able to work out what size door, will fit into the opening you have available. 

If you’re still having difficulty trying to find your correct door measurements then please do not worry. Just give us a call and we would be more than happy to help you.

Trimming advice for our doors

If your closest door size is too small for the frame opening then what you could do is pack out the frame using extra pieces of wood. This will help to reduce the size of the frame opening and will ensure that you have no gaps, when you go about fitting your new door.

Or, if the opposite is true and the closest size door available is too large for the frame then you could trim the door until it fits the space you have. For this job you will need to be a competent joiner or if you have the skills then go ahead yourself! 

When you go ahead with trimming a door down to size there are some guidelines that are worth following, to get the job done properly.

Trimming engineered timber doors


Deanta doors are especially made with extra thick 18mm solid wood veneers. These doors are the best choice for customers looking to take off a greater amount. They will allow you to take off 16mm from each side. You can therefore reduce the door size by a maximum of 32mm. 

All other brands

Each of our other door brands are made with 10mm solid wood veneers. They will enable you to remove 8mm from each side. So, you can remove a total of 16mm altogether.

Trimming White moulded and primed doors

When it comes to trimming white moulded or white primed door, we recommend that you remove no more than 6mm off each side. This is due to the construction of these engineered doors. If they are reduced by more than 6mm then they can become unstable.

Trimming Fire doors

For fire doors, we recommend that they shouldn’t be altered in any way at all. Reducing the size of these could affect the fire rating of the door and so the door wouldn’t stand up to fire safety regulations. If you do need to have your fire door altered then please do not hesitate to get in touch with us and we can help find the right fire door for your needs. 

If you can’t find your size door - Go bespoke!

We, at The Posh Door Company know that not all homes are the same and not all doors will be able to fit into certain spaces in your home. Which is why we are more than delighted to provide our customers with our stunning bespoke doors. The majority of our interior doors can be made bespoke to your requirements and you can look forward to having beautiful new doors that will fit your home and space, perfectly. 

For more information about our bespoke doors, please do not hesitate to get in touch with us and we would be more than happy to help you find your ideal door for your home, which will look absolutely stunning!