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What are the standard sizes for windows in the UK?

It might seem to a layman that windows can come in a huge variety of different sizes, when in fact many manufacturers in the UK work to a standard range of British standard window sizes.

The fairly obvious reason is that as long as standard window sizes stay within a certain range, windows can be bought and installed with the reasonable expectation that they’ll fit the space they’re meant for.  

Using this same logic of standardisation, uPVC window sizes are generally shared with other window materials such as aluminium and timber windows. There are average window heights and window widths that will apply to a wooden window or a UPVC sash window. The average window height and window width in the UK are as follows:

Standard window heights:

450 millimetres (mm)

600 mm

1,050 mm

1,200 mm

1,350 mm

1,500 mm

Standard window widths:

488 mm

630 mm

915 mm

1,200 mm

1,770 mm

Casement windows are the most popular style of window in the UK and also the most versatile window, available in many different configurations. For that reason, the industry doesn’t specify a standard size, although many manufacturers do offer a range of sizes for casement windows.

Common casement window heights are:

890 mm

1,119 mm

Common casement window widths are:

635 mm

736 mm

Common sash window heights are:

609 mm

914 mm

1,219 mm

1,524 mm

Common sash window widths are:

914 mm

1,219 mm

1,524 mm

1,829 mm

2,134 mm

Standard sizes can vary.

Another important reason for having standard window sizes is to ensure that they fit brickwork of a certain length – usually between 215 mm and 300 mm – sizes that have been determined by legislation in the hope of making building practices easier and more standardised. Yet despite some common window sizes in the UK, actual window sizes can and often vary from one property to another of a similar type.

Variations in property ages. 

To further complicate matters there are certain types of window that don’t conform to preset standards because the properties and installations that use them vary in their design periods and the overall age of the building. Even buildings of the same era can feature a variety of window sizes.  

Will it fit the room?   

What’s more, the size – and shape – of a window can have been determined by where it was positioned in the property and the type of room it was made for. Living rooms usually have larger windows, as do conservatories, whereas bathrooms and kitchens have traditionally been designed and built with smaller windows.

Residence Collection – always a perfect fit.

All of that said, part of the beauty of Residence Collection windows is that they are bespoke and can be custom manufactured and made to measure for any style of property, traditional or contemporary, whilst retaining exceptional performance, high security and industry leading low U values.

Start your Residence Journey today. Download one of our brochures or find your local Residence Collection installer.



At Residence Collection, we have a range of colours available and can offer everything from timeless classics like Grained White to modern favourites such as Eclectic Grey. Don’t forget, we also offer a dual finish that allows you to find windows and doors that look as good from the inside as they do outside.