Roof window sizes for pitched and flat roofs

Did you know that daylight is more powerful from above, and that roof windows can provide 2 to 3 times more daylight than facade windows? If you want to reap all the benefits of bringing more natural light into your home with a roof window, it’s important to pick a size that’s tailored to the room’s size, layout, and purpose, as well as your particular roof type.

At VELUX, we offer a wide range of roof window sizes to suit all kinds of roofs and projects, whether you’re giving a tired loft a fresh new feel, adding light to a modern extension, or just making a small bathroom feel that little bit brighter.

VELUX roof windows don’t just open up your space; they open up new ways to enjoy it. From big, open-plan living areas to compact rooms that need a lift, there’s a size that fits. Not sure what you need yet? Let’s take a closer look at how to find the right roof window size for your home.

Get the size of your roof window right, and you’ll notice the difference

The size of your roof window plays a big part in how a room feels. Too small, and you might still find yourself switching the lights on. But get it right, and you’ll bring in just the right amount of daylight to make the space feel bigger, more open, comfortable, and a joy to spend time in.

In fact, 27% of homeowners* would have preferred a bigger roof window than the one they installed. And there are many good reasons for that. By inviting more natural light into the room, you can do great things for your general mood, as exposure to natural sunlight helps regular the body’s internal clock.

It’s not only about light, either, but also about the opportunity to open the room up to your outdoor space and the nature surrounding it. Furthermore, the right size window can help regulate temperature, reduce the need for artificial lighting, and make your home feel fresher and more energy-efficient overall.

^{*VELUX Combi Solution Study by NEPA, Dec 2019-Jan 2020.}

General roof window size recommendations

As a general guide, the window size should be around 15-20% of your room’s floor space if you have a pitched roof, while the recommended size for flat roofs generally should be around 10-15%.

If you already know that the roof window will be subject to shadows and obstruction from outside elements, such as neighboring buildings, a 25-30% roof window to floor ratio would be a good idea.

It’s a simple rule of thumb, but it really helps when you want a room that looks good and feels even better. If you’re uncertain about what roof window size to go for, ask VELUX Advisory Service for a daylight analysis of your room.

Attic bedroom with sloped ceiling and open VELUX roof windows, natural light.

Roof window size recommendations for pitched roofs

As a general guide, the window size should be around 15-20% of your room’s floor space if you have a pitched roof. If you already know that the roof window will be subject to shadows and obstruction from outside elements, such as neighboring buildings, a 25-30% roof window to floor ratio would be a good idea. It’s a simple rule of thumb, but it really helps when you want a room that looks good and feels even better. If you’re uncertain about what roof window size to go for, ask VELUX Advisory Service for a daylight analysis of your room.

Black tiled roof with VELUX window, surrounded by trees and sky.

Roof window size recommendations for flat roofs

For flat roof types with a pitch between 0° and 15°, the right window size can help you transform your space with stunning views and ample daylight, making your home feel larger and more open. The general recommended size for flat roofs generally should cover around 10-15% of the floor area. Flat roof windows are generally less affected by surrounding obstructions, such as neighbouring buildings or trees, than facade or pitched roof windows. This means they still bring in plenty of natural light even in tighter spaces. In cases where shadows are unavoidable, slightly larger windows can help ensure your room stays bright and airy.

Roof window size recommendations for low-pitched roofs

If your roof has a shallow pitch—between 10° and 20°—you’ll need a special low-pitch roof window. VELUX offers specially designed low-pitch roof window models to maintain excellent insulation, drainage, daylight intake, and add fresh air to your house extension, even when the roof angle is flatter than usual. Low-pitch windows are designed to let in more light than a vertical window, so you can achieve bright, airy spaces even with a smaller footprint. For low-pitch roof windows, we also generally recommend you aim for 15–20% of the room’s floor area — just as with roofs that have a broader pitch above 20°.

Understanding VELUX roof window sizes

VELUX makes it simple to choose the right window for your project. Our different roof windows suited for various homes and roof types come in a range of carefully considered sizes, with coded labels to help you easily identify them. These codes tell you exactly what size the window is, meaning you can pick new windows with confidence or find a perfect replacement for an older VELUX model.

Our different sizes for pitched and flat roof windows cover everything from compact spaces needing a little more light to larger rooms that benefit from floor-to-ceiling glazing and dramatic views of the outdoors. Often windows are combined into a double installation, to ensure an optimal daylight influx and a great view and connection to the outdoors.

Here’s a quick guide to some of our sizes:

Size code and window size (width x height)

FK06 - 66 cm x 118 cm
MK04 - 78 cm x 98 cm
MK06 - 78 cm x 118 cm
MK08 - 78 cm x 140 cm
PK06 - 94 cm x 118 cm
PK08 - 94 cm x 140 cm
SK06 - 114 cm x 118 cm
SK08 - 114 cm x 140 cm
UK04 - 134 cm x 98 cm
UK08 - 134 cm x 140 cm

These sizes cover everything from compact spaces needing a little more light to larger rooms that benefit from floor-to-ceiling glazing and dramatic views of the outdoors. Often windows are combined into a double installation, to ensure an optimal daylight influx and a great view and connection to the outdoors.

(Note: This is a selection of some of our window roof sizes – more options are available)

Dowload size table

Poster with VELUX roof windows (product size chart) Standard roof windows and Special function roof windows

Person opening a VELUX roof window, allowing fresh air and light.

Roof window sizes, endless flexibility

While our roof window sizes cover most homes and projects, there’s always room to get creative. You can:

Combine multiple roof windows for a larger glass area and a panoramic view
Add fixed elements below your opening window for a stunning floor-to-ceiling effect

The possibilities are endless. Whether you’re planning a single window or a dramatic feature wall of glazing, VELUX has the sizes and styles you need to bring your vision to life.

Attic room with VELUX roof windows, sloped ceiling, and cozy seating.

Find the ideal pitched roof window size for your room type

Every room in your home with a pitched roof can benefit from the right window size:

Attic kids room with sloped ceiling and VELUX roof windows with roller shutter, natural light.

Bedrooms and kids’ rooms

Bedrooms and kids’ rooms: Consider a double window with e.g. 2 x MK08 windows (2x78 cm x 140 cm) installed right next to each other. This option creates a light airy atmosphere and an amazing connection to nature outside. Plus, smaller rooms will feel an added spaciousness

Modern bathroom with sloped ceiling and VELUX roof window, bright and airy.

Bathrooms

A single roof window can bring in increased natural light and control ventilation while maintaining privacy. For tranquility, go with a larger single window or duo combination to bring nature in. You can also add a moisture-resistant blind for extra privacy. As the bathroom is known for being a room with high humidity levels, it’s key to choose a VELUX roof window with a maintenance-free finish.

Attic room with large VELUX roof windows, natural light and modern decor.

Living rooms

Go big! Combine a couple of PK08 (94 cm x 140 cm) or UK08 (134 cm x 140 cm) windows. Alternatively, go for our trio or quattro window combinations for a light-filled place with daylight, connection to the outside, and wow-factor.

Dining room with VELUX roof windows, black chairs, and garden view.

Kitchens

A double or triple window combination above your worktops lets in both daylight and ventilation, making the space feel fresh and inviting. As kitchens often can become rather humid when you cook, a roof window with a maintenance-free finish is a must-have.

Attic room with sloped ceiling and large VELUX roof windows, natural light entering.

Home offices

A double window will make the room feel spacious and bring daylight right where you need it to help boost focus and productivity. For optimal indoor comfort and working conditions add an awning blind to maintain a comfortable room temperature or translucent blind for a flexible light dimming solution

Remember, you can always combine several windows for even greater impact. Our Duo and Triple roof window combinations, for example, pair or triple up windows for more light, better views, and a modern architectural finish.

Transforming every room in your flat-roof home

Just like our roof windows for pitched roofs, different spaces in your flat-roof home can benefit from a window size that’s tailored to the room:

Family in a bedroom with a VELUX roof window and modern decor.

Bedrooms and kids’ rooms

For bedrooms and children’s rooms, consider a flat roof window around 90 cm x 90 cm. This size brings in ample light and can also enhance airflow for improved sleep quality if you choose a vented, solar-powered, or electric roof window model. For larger rooms or loft spaces, combining two flat roof windows of 90 cm x 120 cm will further boost daylight and create a more spacious atmosphere.

Modern bathroom with VELUX roof window, wooden ceiling, and walk-in shower.

Bathrooms

A 80 cm x 80 cm window is a great choice for bathrooms, offering plenty of natural light. To enjoy the added benefit of natural ventilation, choose one of our vented models to prevent moisture from building up, or our solar-powered or electric flat roof window options, which let you remotely open and close the window to let in fresh air when you want to. For larger bathrooms, a 90 cm x 120 cm flat roof window can ensure the space feels fresh and bright and really sells the feeling of getting ready or taking a bath right under the open sky.

Modern kitchen with VELUX roof windows and dining area.

Kitchens

For kitchens, where light and ventilation are key, a 90 cm x 120 cm or 100 cm x 150 cm flat roof window provides excellent daylight while keeping the room fresh. Larger vented roof windows or our solar-powered or electric options are particularly beneficial in kitchens that can become warm, as they offer natural temperature regulation and help get rid of moisture and unwanted cooking smells.

For the best use and effect of a flat roof window in your kitchen, consider slightly offsetting the window instead of placing it directly over your countertop to brighten your work areas without standing in your own shadow when cooking.

Living room with flat ceiling and VELUX roof windows, sunlight entering.

Living rooms

In living rooms, larger flat roof windows such as 200 cm x 60 cm or 200 cm x 100 cm provide generous light throughout the day and give you a front row view of the sky above - or perhaps a peek of the tree tops outside where you can follow the seasons change. Combining two 90 cm x 120 cm flat roof windows further enhances the connection to the outdoors, creating a stunning visual impact and a bright, welcoming living area.

Contemporary hallway with VELUX roof window and minimalist decor.

Hallways/entryways

Hallways often benefit from larger flat roof windows or window combinations to create a brighter and more inviting entrance. Consider a 90 cm x 120 cm or 100 cm x 150 cm window for a significant increase in natural light. For even more impact, you can combine multiple windows to create a dramatic effect that floods the hallway with daylight, making it feel spacious, welcoming, and airy. Larger windows also help visually connect the interior with the outdoors, enhancing the overall ambiance of your home’s entrance.

Home office

A 80 cm x 80 cm or 90 cm x 90 cm flat roof window is ideal for home offices, offering plenty of natural light to improve focus and productivity. For better comfort, consider pairing the window with an awning or translucent blind to regulate the room’s temperature and light.

Quick guide: How to choose your VELUX window size

Measure your room: Aim for a window solution corresponding to 15-20% of your floor area for pitched roof windows or 10-15% for flat roof windows.
Think about usage: Go for bigger windows or window combinations for primary rooms like bedrooms, kids' rooms or living rooms where you spend important time. For less used, smaller rooms, a more compact option is often more popular.
Consider the ways of operating the windows: You can upgrade both our pitched and flat roof windows to solar-power or electric for extra comfort and convenience. Alternatively, you can choose a manual version for our pitched roof windows or a fixed version for our flat roof windows if you prefer. You can supplement your solar-powered or electric roof window with our VELUX App control, for full smart home control of your roof windows.

To further enhance the control of your indoor climate, you can combine your pitched roof windows with interior blinds for light control, and exterior awning blinds or shutters for heat protection. For our flat roof windows, interior blinds are available with options such as semi-transparent fabrics, blackout fabrics, or anti-heat coatings to help manage light and indoor temperature.

Attic living room with sloped ceiling and large roof windows, cozy seating area.

Ready to find the right fit for your home?

At VELUX, we believe that more daylight, more fresh air, and better living starts with the right roof window – and that all begins with finding the right size.

Whether you're replacing an old window or starting a brand-new project, our roof window sizes give you the flexibility and choice to create the home you've always dreamed of.

Explore the full range of VELUX windows and discover just how easy it is to transform your space. Need a little help? Contact our team for expert advice, or check out our Design Advisory service to get personalised recommendations for your project.