VELUX Window Sizes Made Easy - Velux Size Guide

Posted by Skye Tunks on 31st January 2020

Why not make shopping for your new windows even easier? 

In this blog, we are going to go through our exclusive VELUX Window Size Guide, because as we all know, it can be confusing with the different range of sizes, model numbers and window codes that are applied to each one.

Let’s discover your exact window match now, it will only take a few minutes.

Firstly, you must know the exact measurements available and with our size guide, you can see below the exact sizes from which you can choose from.

Click our interactive VELUX size chart below to view all products in below VELUX sizes.

 55cm 66cm 78cm 94cm 114cm 134cm
 70cm CK01 SK01 
 78cm CK02
 98cm CK04 FK04 MK04  PK04  UK04
 118cm CK06  FK06 MK06  PK06 SK06 
 140cm  FK08 MK08  PK08  SK08  UK08
 160cm MK10  PK10  SK10  UK10
 180cm MK12 

If you are looking to replace an existing VELUX roof window, then you can easily use the size guide above to see which new generation code relates to your old roof window code (compare with the diagram below) to determine your VELUX window sizes.

To explain, if your current VELUX branded window has a code of GGL2, then your new VELUX windows would now have the code MK08. For an even further explanation, take another review of the diagram above and compare your old code, to the new.


A Guide to your VELUX Window Codes and Sizes.

It's a known fact that VELUX is always improving their products, to help ensure that they maintain the high quality that they are known for. These continuous improvements over the years have resulted in some of the older styles becoming out of date in terms of shelf life.

However, this is not a problem, as the new off-shelf VELUX flashings can be made to fit any older window, in many circumstances.

Here are the old VELUX sizes, serial number, and number codes -

  • Window size 55 (W) x 78 (H) code 102 or C02 or CK02

  • Window size 55 (W) x 98 (H) code 104 or 6 or C04 or CK04

  • Window size 78 (W) x 98 (H) code 304 or 1 or M04 or MK04

  • Window size 66 (W) x 118 (H) code 206 or 5 or F06 or FK06

  • Window size 78 (W) x 118 (H) code 306 or 14 or M06 or MK06

  • Window size 78 (W) x 140 (H) code 308 or GGL2 or M08 or MK08

  • Window size 134 (W) x 98 (H) code 804 or 7 or U04 or UK04

  • Window size 114 (W) x 118 (H) code 606 or 4 or S06 or SK06

  • Window size 94 (W) x 160 (H) code 410 or 3 or P10 or PK10

  • Window size 134 (W) x 140 (H) code 808 or 8 or U08 or UK08

For example. A VELUX GGL4 will be replaced by VELUX code SK06. VELUX replacement flashings can be used to replace the roof window to minimise internal plasterboard alterations.

Above, is the list of window sizes and code varieties that they may have on them, but this all depends on when the window was purchased.

But do remember that window sizes are for the external window frame and not internal measures.

These are strictly VELUX pitched roof window sizes. Not VELUX flat roof window sizes.

Where Are Velux Brand Window Codes Located?

You can easily find VELUX window codes on the top right-hand edge of the roof window when you open it. The data plate tells you the type of window it is, and the window size shown through the code (as seen below.)

As shown in the above example, 304 would be 78cm x 98cm and the bottom window code 4, would be 114cm x 118cm.

Finding your VELUX structural opening size is critical to the install of your roof window. Here is a breakdown on your structural opening size for your VELUX roof window. 

Replacing your roof window. 

When shopping our store for VELUX roof windows. If you’re replacing your roof window it is important to remember that you can change cosmetic features such as the operation (21U, 30), internal finish (GGL, GGU) and glazing (70,68,66......). However, you cannot change the VELUX window size. The VELUX window size code determines your new replacement roof window. For example, if you are replacing a GGL -4, you could change to white painted, triple glazed top hung. However, we recommend sticking to the replacement size. GGL -4 + SK06. So, your replacement would be a GGL SK06 2068. 

(RED) Standard VELUX flashings. Your structural opening size should be the VELUX window should go as the following. 

VELUX Structural opening size = VELUX window external frame dimension (H) + 45mm overall top to bottom. VELUX window external frame size (W) + 20-30mm at each size of the window (Left & Right)

(BLUE) Standard VELUX flashings. Your structural opening size should be the VELUX window should go as the following. 

VELUX Structural opening size = VELUX window external frame dimension (H) + 145mm overall top to bottom. VELUX window external frame size (W) + 25-30mm at each size of the window (Left & Right)

Finding the structural opening size of your Velux window is easy! Begin by measuring the outer frame of your window. The size of the structural opening will be slightly smaller than the window frame size. Next, use a tape measure to measure the height and width of the window opening. Be sure to measure from the exterior wall surface to the interior wall surface. You should now have the dimensions of your structural opening size!

Can't find your VELUX code?

Do not panic. Let us do the hard work! We recommend measuring the visible VELUX glass size on your roof window. (W)cm x (H)cm and take an image of the roof window. You can then forward these details into Although the VELUX glass size does not give us the exact external frame measurement. It gives us a rough guide. Our sales team will try our hardest to find your perfect, new, stylish roof window!

Why choose VELUX?

VELUX is the leading roof manufacturer in the world. Dating all the way back to 1942, their manufacturing and product design is desirable by everyone. VELUX have a huge range of roof window sizes for both pitched roof windows and flat roof windows. VELUX define the market with high quality affordable roof windows to double your daylight in your home.

Not looking for VELUX today?

Our brand portfolio is one of biggest and most diverse in the roof window industry. From huge stock lists from brands of every price point. YARD Direct have you covered. Why not try our window butler to help you find your perfect roof window size today.

If you would like any further information with anything related to roof window repairs, fitting a new flashing set to an old roof and VELUX windows, or how to replace an old VELUX flashing, then please feel free to visit here to find out more, or visit our Window Butler where you will be guided to the perfect window for your project.