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Velux size codes such as CK04, MK04 and PK10 can look confusing at first. Here’s how to compare dimensions, room suitability and offer details before you buy.
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Velux window sizes are usually compared by code as well as by stated dimensions. That is helpful once you know what the codes mean, but it can be misleading if you compare only the headline price. A CK04, MK04 or PK10 listing may refer to a roof window, a flashing kit, a glazing option or an accessory, depending on the retailer’s product title and specification.
The current Windows catalogue includes a mixture of Velux roof window-related listings, from compact 55 x 78 cm options to larger 94 x 160 cm models, alongside accessories such as a telescopic pole. Use those listings as a comparison starting point, then check the exact product contents, opening style, glazing and compatibility before ordering.
Velux codes are useful shorthand, but the stated dimensions are what matter for planning. In the available listings, CK02 is shown with 55 x 78 cm, CK04 with 55 x 98 cm, MK04 with 78 x 98 cm on one listing, and PK10 with 94 x 160 cm. Another Velux MK04-related listing is shown with 78 x 118 cm, which is a good reminder to check every retailer’s title and specification carefully rather than relying on the code alone.
For most shoppers, the safest approach is to treat the code and dimensions as a pair. If either looks inconsistent, pause and confirm whether the listing is for the full roof window, a flashing kit, a replacement part, or a bundle. This is especially important in Windows, because accessories and installation components can appear alongside complete roof windows in search results.
The compact Velux options in the catalogue snapshot include a CK02 EDW 2000 listing at 55 x 78 cm and CK04-related listings at 55 x 98 cm. These narrower sizes can make sense where rafter spacing, roof layout or room proportions limit what will fit. They are often the first sizes shoppers consider for small loft rooms, landings, compact bedrooms, bathrooms or utility spaces, subject to building layout and installer advice.
A key comparison point is height. Moving from 55 x 78 cm to 55 x 98 cm keeps the same listed width but gives a taller unit, which may help bring light lower into the room or improve the sense of openness. However, the best choice depends on where the window sits in the roof slope and how the room is used, not just on the biggest size you can find.
The price difference in the supplied catalogue is not enough on its own to make a decision, because some lower-priced Velux EDW listings may be flashing-related rather than a complete window. When comparing offers, read the product title and included components before assuming one CK size is dramatically cheaper than another.
MK04 is one of the most useful comparison points in the available listings because it sits between compact CK sizes and larger PK sizes. One Velux MK04 EDW 2000 listing is shown at 78 x 98 cm, while another Velux MK04 EDW 2000 triple-pane listing is shown with 78 x 118 cm. That difference is exactly why shoppers should check both code and dimensions, then cross-check the product description before buying.
A 78 cm-wide roof window can feel more generous than a 55 cm-wide option, particularly in a bedroom, study or loft conversion where daylight matters throughout the day. It may also be easier to balance with furniture layout because the window can become a stronger feature in the room rather than a small light source high in the ceiling.
When comparing MK04 offers, also look at the wording around glazing. The catalogue includes references to double-pane and triple-pane on different Velux listings. Do not assume those terms mean the same product type, performance or included parts across every retailer; use them as prompts to examine the specification in more detail.
The largest Velux listing in the supplied set is a PK10 GGL 2070 aluminium tilt window at 94 x 160 cm. A size like this is a very different proposition from a compact CK window. It is more likely to suit a larger loft room, open-plan upper floor, studio space or main bedroom where the goal is to make daylight a defining feature.
The trade-off is that larger roof windows need more careful planning. You will want to consider roof structure, internal headroom, the height of the handle or operating point, blind compatibility, and whether the window can be opened comfortably. For some projects, two smaller roof windows may offer more balanced light than one large unit; for others, a single larger window may create the cleaner look.
Because larger listings usually involve a higher overall spend, compare the complete project cost rather than the window price alone. Flashing, installation materials, blinds, poles or electric operation accessories can all affect the final budget.
One of the easiest mistakes is comparing a full roof window against a flashing kit or accessory. In the supplied product candidates, there is also a telescopic pole for Velux skylights, shown separately from the windows. A pole may be essential if a roof window is out of reach, but it is not a substitute for the window itself.
The Velux EDW wording in some listings should prompt extra checking. Flashing products are used around roof windows to help fit them into suitable roof coverings, while the window itself may be listed separately or as part of a bundle. Retailer titles can be short, translated or merchandising-led, so always check the included items before treating a low price as a complete roof window bargain.
This matters when comparing offers across Windows, Roof Windows and Tilt Windows. A listing with a strong discount signal is useful to investigate, but the best-value option is the one that matches your roof, room, installation requirements and included components.
The catalogue includes Velux tilt-style wording, and the wider Windows category also includes Side-Hung Windows, Top Hung Windows, Sliding Windows, Fixed Windows and Sun Tunnels. For roof spaces, opening style affects everyday use as much as size. A window that is too high to reach may need a pole or powered operation, while a window above furniture may need a different placement or opening type.
For bathrooms and kitchens, ventilation may be a priority, so a usable opening window is often more practical than a fixed option. For a stairwell, landing or dark corridor, the main goal may simply be borrowed daylight, in which case Sun Tunnels or smaller roof windows may be worth comparing. For a bedroom or home office, daylight, view, glare control and blind options are likely to matter more.
If you are replacing an existing Velux window, the easiest route is often to compare like for like using the existing plate or code, while still confirming the modern equivalent and the full specification with the retailer or installer.
First, shortlist by size: compact CK02 or CK04 for smaller spaces, MK04 for a more generous mid-size option, and PK10-style dimensions for larger rooms. Then compare the stated dimensions, not just the code.
Second, check what the offer includes. Is it a complete roof window, a flashing kit, glazing unit, accessory or a package? A lower catalogue price can be attractive, but it is only comparable if the included components are equivalent.
Third, compare glazing and finish details where provided. The supplied listings mention double-pane and triple-pane wording, plus materials such as aluminium and wood on different products. Treat those as specification clues to investigate rather than automatic proof that one listing is better.
Finally, factor in practical extras. Blinds, poles, window sills, shutters and fitting components can all change the final cost and usability. Comparing products and offers side by side helps you spot whether one retailer’s headline price is genuinely useful for your project or simply covers a different part of the job.
They are size codes used to identify Velux roof window dimensions. In the supplied listings, CK04 is shown at 55 x 98 cm, MK04 appears on listings around 78 cm wide, and PK10 is shown at 94 x 160 cm. Always check the stated dimensions and product contents before buying.
Not always. A larger roof window can bring in more daylight, but it also needs suitable roof space, comfortable operation and a sensible position in the room. Smaller windows can work well in bathrooms, landings and compact loft rooms, while larger sizes may suit bedrooms, studios and open-plan spaces.
Some listings may be for flashing kits, accessories or related components rather than a complete roof window. Check the title, specification and included items before comparing prices.
A compact size such as 55 x 78 cm or 55 x 98 cm may be easier to accommodate in a small room, depending on the roof structure and layout. The right choice also depends on the window position, ceiling slope and how much daylight or ventilation you need.
A roof window can provide daylight, outlook and ventilation if it opens. A sun tunnel is usually considered where a conventional roof window is not practical or where the goal is to brighten an internal space. Compare both options if you are improving a dark landing, corridor or small room.
The best Velux size is not simply the largest one or the cheapest listing in the catalogue. Start with the room, then compare code, dimensions, opening style, glazing wording and included components.
For many shoppers, CK sizes suit smaller spaces, MK sizes offer a useful middle ground, and PK sizes are better reserved for larger rooms or more ambitious loft projects. Before you buy, compare the relevant Windows and Roof Windows offers carefully so you know whether you are looking at a complete window, a flashing kit, or an accessory that forms only part of the installation.
