What Are Standard Window Sizes
Understanding Standard Window Sizes:
Why One Size Doesn’t Fit All
There are so many unique homes across the UK, in all sorts of shapes and sizes, which means standard window sizes don’t always apply. Window dimensions often depend on the type, style, and age of your property, and they can vary significantly.
One of the main benefits of professional installation is that fitters will measure your openings precisely to ensure a perfect fit. Getting the sizing right is essential to avoid any unwanted gaps.
In this guide, we’ll walk you through some size charts for common window types, but first, let’s answer a key question:
What are standard window sizes?
Explore Window Sizes
Discover how window dimensions vary depending on style, material, and where they’re used in the home.
Standard UPVC Window Sizes
UPVC is the most common window material chosen for UK homes, largely due to its durability and cost effectiveness, with double glazed being the most common choice of glass when it comes to triple glazing vs double glazing vs single glazing. The standard double glazed window sizes are shown below:
UPVC Window Standard Heights:
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500 mm (19.7 in)
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600 mm (23.6 in)
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1050 mm (41.3 in)
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1200 mm (47.2 in)
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1350 mm (53.1 in)
UPVC Window Standard Widths:
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488 mm (19.2 in)
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630 mm (24.8 in)
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915 mm (36 in)
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1200 mm (47.2 in)
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1770 mm (69.7 in)
Standard Casement Window Sizes
Casement windows are a classic window style that are known for being extremely versatile. They are the most popular window designs in the UK, and therefore they are available in a variety of configurations for all different openings.
Typical sizes for Casement Windows:
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635 mm × 890 mm (25 × 36 in)
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736 mm × 1194 mm (29 × 74 in)
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736 mm × 1498 mm (29 × 59 in)
Standard Tilt and Turn Window Sizes
Tilt and turn windows are unlike any other window offering on the market – they’re easy to clean and offer homeowners incredible control over ventilation, which is particularly important in the summer months. Typical sizes for single, double and triple tilt and turn windows are:
Single Tilt and Turn:
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Min: 600 mm × 500 mm (23.6 × 19.7 in)
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Max: 1900 mm × 1300 mm (74.8 × 51.2 in)
Double Tilt and Turn:
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Min: 600 mm × 1200 mm (23.6 × 47.2 in)
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Max: 1700 mm × 2400 mm (66.9 × 94.5 in)
Triple Tilt and Turn:
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Min: 600 mm × 1600 mm (23.6 × 62.3 in)
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Max: 1900 mm × 3000 mm (74.8 × 118.1 in)
Standard Sash Window Sizes
Sash windows beautifully replicate traditional windows of bygone eras. Despite their modern performance, they look perfectly at home at cottages and country residences due to their distinct look. They are also favoured for adding a touch of character to modern properties.
Sash Window Standard Widths:
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914 mm (36 in)
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1219 mm (48 in)
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1524 mm (60 in)
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1829 mm (72 in)
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2134 mm (84 in)
Sash Window Standard Heights:
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609 mm (24 in)
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914 mm (36 in)
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1219 mm (48 in)
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1524 mm (60 in)
Standard Bay Window Sizes
When it comes to double glazing windows, the bay window is a favourite because it creates a focal point from the exterior and welcomes lots of natural light in your interiors. They protrude outwards, making your room look larger and seating can also be added to create a window seat. Take a look at the bay windows’ standard window sizes cm below:
Bay Window Standard Widths:
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Min: 1016 mm (3 ft 6 in)
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Max: 3200 mm (10 ft 6 in)
Bay Window Standard Heights:
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Min: 914 mm (3 ft)
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Max: 1981 mm (6 ft 6 in)
Window Sizes
Room-by-Room
Bathroom
Bathroom windows are usually smaller, designed to ensure privacy while still letting in some natural light. They’re often placed higher up on the wall to balance light, discretion, and ventilation in the space.
Bathroom windows are usually smaller, designed to ensure privacy while still letting in some natural light. They’re often placed higher up on the wall to balance light, discretion, and ventilation in the space.
Living Room
Living room windows are often the largest in the home. They are designed to let in maximum natural light and help create an open, bright, and welcoming atmosphere.
Living room windows are often the largest in the home. They are designed to let in maximum natural light and help create an open, bright, and welcoming atmosphere.
Kitchen
Kitchen windows are typically placed above the sink and are shorter in height. They still prioritise natural light, especially in open-plan spaces, to keep the area feeling bright and practical.
Kitchen windows are typically placed above the sink and are shorter in height. They still prioritise natural light, especially in open-plan spaces, to keep the area feeling bright and practical.
Bedroom
Bedroom window sizes vary depending on layout and style. Some rooms feature large windows for morning light, while others use smaller ones to create a cosy, restful environment.
Bedroom window sizes vary depending on layout and style. Some rooms feature large windows for morning light, while others use smaller ones to create a cosy, restful environment.
Material-Based Differences in Standard Sizes
The material you choose for your windows can influence the standard window sizes available, as well as how much flexibility you have with the design.
UPVC – Coloured UPVC windows tend to follow the most common standard sizes, making them a popular and cost-effective choice for modern homes. The standard UPVC window sizes and their dimensions often align with typical UK window openings, which makes replacements straightforward.
Timber – Timber windows are often custom-made, especially in period properties or conservation areas. They’re usually tailored to suit the original style and proportions of the home, which means standard sizing doesn’t always apply.
Aluminium – Thanks to its inherent strength, aluminium allows for slimmer frames and larger expanses of glass. Replacement aluminium windows are ideal for creating wide or tall windows, perfect for letting in lots of natural light without compromising on stability.
How to Measure Your Windows Properly
If you’re planning to replace your windows and want to get a rough idea of the sizes you’ll need, measuring them correctly is a great place to start. Here’s a simple 4-step guide to help you do just that.
Measure from the outside
Use your tape measure to take all dimensions from the outside of your property. Measuring from the external brickwork provides the most accurate results and avoids any confusion caused by internal finishes or angles.
Take three measurements
Measure the width of the window opening at the top, middle, and bottom. Then measure the height at the left, centre, and right sides. Use the smallest width and height to ensure your new window fits the opening without any gaps or issues.
Check for squareness
To check if the opening is square, measure diagonally from corner to corner in both directions. If the measurements are similar, your opening is square. Significant differences mean the area may need adjustment or special attention during installation.
Allow for fitting tolerance
Always subtract 5–10mm from the smallest width and height to allow space for fitting. This fitting tolerance gives the installer enough room to adjust the frame during installation and ensures a smooth, secure fit.
Summary: Key Points about Standard UK Window Sizes
We hope you’ve found this guide helpful in understanding average window sizes in the UK. Whether you’re embarking on a full home renovation or replacing a single window, knowing the standard sizes is just the beginning – and we’re here to support you every step of the way.
Remember, the expert team at Hazlemere will carry out accurate measurements to ensure your new windows fit just right, as well as ensuring they remain in keeping with the style and age of your property. When replacing your windows, we understand you might have a lot of questions because it’s a big investment for your home.
For other window-related questions such as finding out what is a good u value for your windows, head to our blog for our expert guidance as always.
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