Sizing Guide & How To Measure

Size Guide and Measuring Your Door

Doors are supplied in industry standard sizes OR in some cases can be made to Bespoke sizes, the starting point is always to measure the opening that you have (i.e. the size of the space where the door will go). Our doors can be adjusted down in size by 6mm on all edges to allow for a proper fit, so 12mm on the width and at least 12mm on the height can be removed to allow for fitting.

When you are working out the door size remember that there needs to be a 2 – 3mm gap around the door to allow it to open and close and so selecting the correct door and fitting it is more of an art than a science. Also allow for the fact that doorways are typically built by human beings and so may not be exactly square and true, it is best to measure in a couple of places and take an average, don’t worry about the variation, it’s why our doors can be adjusted.


Can I measure the door that’s in the hole already?

The simplest way to measure the door that you need is to measure the old one if it’s still hanging, but remember to check that it fits properly and doesn’t rub on the frame or have huge gaps around the sides and tops. If you are happy with the way the existing door is fitted then go ahead and measure it and then make your selection, if in doubt or if you are going to be upgrading the frame, measure the hole in the wall instead.


Measuring the hole in the wall

The opening that you have in the wall will either already have a frame fitted or will just be a bare opening, when you measure a bare opening the size you have is known as the “Brick to Brick opening”, or “Brick opening”.

If you are measuring an opening that already has a frame fitted then this measurement would be described as “frame to frame”.

Once you have your frame to frame or brick to brick opening measurements the simplest way forward would be to contact one of our Door Experts and let them confirm the door size that is best for you.

If you prefer to do the calculations yourself then there is a list of popular External and Internal door sizes.

Allowing for adjustments and frames

To confirm what will be suitable look at the standard heights and widths on the chart and find the closest to the frame to frame opening size that you have, remember all of our doors may be cut down by 6mm on each edge and so you have 12mm of adjustment possible on the width of all doors. Heights can often be cut down by a lot more but it depends on the style and construction of the door you have selected and so we would prefer to discuss this with you and confirm what can be removed beyond 12mm on the height.

If you are working with Brick to brick measurements (there is no frame in the hole) then you will need to allow for the frame as well as the door, this is simpler than it sounds if you are using our components as External frames have a 40mm section and internal frames have a 30mm section – see diagrams below.

So on an external Brick opening you would add 80mm to the width and the height of the door to get close to the brickwork and on Internal doors you would add 60mm to the width and just 30mm to the height of the door to get near to the brick to brick opening.

Our Door Experts are used to dealing with the awkward sizes that people throw at them, if they are clear on whether you have given them the brick to brick opening size or the frame to frame opening size then they will be able to advise you properly.

Do I need a bespoke size door?

It is very unusual for someone to need us to build a door to a non industry standard size if it is replacing an existing door. Our aim is always to find you the most cost effective way to source and fit a door. If all else fails we can reach into our bag of tricks and find a bespoke solution, but we rarely have to, we have a far wider range of door sizes available to us than most and we can typically find you a solution.

Bespoke doors though come into their own when you want to make a statement, either with much taller doors than standard or wider doors than standard. We have solutions for all sorts of projects and many of us take great delight in helping configure truly bespoke doors for innovative homes. If you want something special give us a call and we will help you make it a reality.

If you are stuck and unsure, our dedicated Door Experts are on hand to help with any information you need. Simply use our Live Chat to speak with us right away, or alternatively call us on 0800 633 5050, or email us at

Our Door Experts are always on hand to help with any questions or queries you may have about any of our products. You can contact us using the methods below.

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