WHAT SIZES DO VELUX ROOF WINDOWS COME IN?

VELUX roof windows come in a range of standard sizes, identified by fixed size codes such as CK01, MK04, MK08 and UK10. Sizes range from compact options like 550mm x 700mm up to larger roof windows such as 1340mm x 1600mm, designed to suit common UK roof openings.

Use this guide to find the right VELUX size code, understand what the codes mean, and identify the correct size for replacements or new installations.

HOW VELUX WINDOW SIZES WORK

VELUX roof windows are manufactured in standard sizes. Each size is identified by a code (such as MK04) that maps to a fixed width and height.

• Each size code refers to a fixed window size (width and height)
• The size code stays the same even if you change glazing or finish
• For like-for-like replacements, matching your existing size code is usually the easiest option

MOST COMMON VELUX WINDOW SIZES IN THE UK

If you want the quick answer, these are the VELUX roof window sizes most commonly used across UK homes and loft conversions.

FULL VELUX ROOF WINDOW SIZE CHART

Use the chart below to match your roof opening to a typical VELUX size code range.

WHAT DO VELUX CODES MEAN?

A VELUX window product code typically includes:

• Window type (for example, GGL = centre pivot)
• Size code (for example, MK08)
• Variant (glazing, finish, or specification)

The size code never changes. You can often change the type or glazing when replacing a window, but the size must match the roof opening unless you are altering the structure.

HOW TO FIND YOUR EXISTING VELUX WINDOW SIZE

If you’re replacing a window, the quickest way to confirm the size is by checking the data plate:

1. Open the roof window fully
2. Look at the top right-hand corner of the sash
3. Find the metal ID plate
4. Note the size code (for example, MK04)

VELUX CONSERVATION WINDOW SIZES

VELUX conservation windows are designed for heritage and listed buildings and are available in a smaller range of sizes.

VELUX 2-IN-1 & 3-IN-1 WINDOW SIZES

VELUX combination windows group multiple sashes into one frame, giving you more daylight and wider views:

• 2-in-1 windows typically range from 1270mm to 1550mm wide
• 3-in-1 windows can reach widths of up to 1880mm
• Heights often match popular formats such as MK06 or MK08

CAN YOU CHANGE A VELUX WINDOW SIZE

For like-for-like replacements, the size code should stay the same. Changing the size usually means altering the roof structure.

• You can change glazing, finish, and sometimes window type
• You cannot change the size without structural work

CONCLUSION

VELUX roof windows come in standard sizes identified by a size code. By checking your existing data plate or using the size chart above, you can confidently choose the right replacement window size and avoid costly mistakes.

FAQs

Are all VELUX window sizes standard?

Yes. VELUX roof windows are manufactured in standard sizes, each identified by a size code (for example, MK04). The code maps to a fixed width and height.

What is the most popular VELUX size in the UK?

MK04 (780mm x 980mm) is one of the most common VELUX roof window sizes in the UK and is frequently used in loft conversions and replacement projects.

Can I measure the opening instead of using the size code?

You can measure the opening, but it’s usually best to confirm the size code from the window data plate first. Measurements can be affected by trims and installation details.

Does the size code change if I change glazing or finish?

No. The size code stays the same. Glazing and finish are part of the variant, while the size code refers to the fixed window dimensions.

Can I change a VELUX window size without changing the roof opening?

Not usually. If you are keeping the same roof opening, the size code should match your existing window. Changing size typically requires structural alterations to the opening.