Are There Standard UK Door Sizes?

Common Internal Door Sizes in the UK

Internal doors are commonly available in a range of traditional imperial and metric sizes. The table below shows some of the most common dimensions found in UK properties.

Imperial / Metric Door Size Conversion Chart

Imperial (inches) - H x W	Imperial (feet & inches) - H x W	Metric Door Sizes - H x W
78 x 18”	6'6" x 1'6"	1981 x 457 mm
78 x 21”	6'6" x 1'9"	1981 x 533 mm
78 x 24”	6'6" x 2'0"	1981 x 610 mm
78 x 27”	6'6" x 2'3"	1981 x 686 mm
78 x 28”	6'6" x 2'4"	1981 x 711 mm
78 x 30”	6'6" x 2'6"	1981 x 762 mm
78 x 33”	6'6" x 2'9"	1981 x 838 mm
80¼ x 24⅝"	6' 8¼" × 2' 0⅝"	2040 x 626 mm
80¼ × 28⅝"	6' 8¼" x 2' 4⅝"	2040 x 726 mm
80¼ x 32½"	6' 8¼" x 2' 8½"	2040 x 826 mm

Important Note: Manufacturers sometimes list nominal door sizes rather than exact manufactured dimensions. Nominal door sizes are the standard measurements of the door leaf/slab, excluding the door frame and brickwork opening. Therefore, you should always check the product specification before ordering.

Metric and imperial door sizes are not directly interchangeable. For example, a common metric internal door height is 2040 mm, compared with the traditional imperial height of 1981 mm (6ft 6 in).

Traditional imperial internal doors are typically 35 mm thick, whereas metric internal doors are usually 40 mm thick. Always check the exact height, width and thickness before ordering a replacement door.

External Door Sizes in the UK

External doors differ from internal doors because they are often supplied as complete doorsets and can be manufactured to fit a much wider range of openings.

Many manufacturers supply composite, UPVC, timber and aluminium external doors on a bespoke basis. As such, there is less reliance on a fixed range of standard sizes, and customers can instead choose a door manufactured to suit their opening.

The overall dimensions available will depend on the door material, style and configuration. We cover the minimum and maximum sizes available across our made-to-measure external door range later in this guide.

Are There Building Regulations for Door Sizes?

The Building Regulations 2010 do not set a single standard height or width that applies to every door. However, individual requirements and Approved Documents can affect door dimensions and performance in certain situations, particularly in relation to accessibility, fire safety, energy efficiency and security.

Jurisdiction note: The Approved Documents referenced below apply primarily to building work in England. Building regulations and supporting guidance differ across Wales, Scotland and Northern Ireland.

Building Regulation Part	Relevance to Door Sizing
B – Fire Safety	Part B includes fire safety requirements that can affect doorsets, including their required fire resistance and the provision of doors on escape routes. It does not prescribe a universal door width or standard door-leaf thickness.
E – Resistance to Sound	Part E covers resistance to the passage of sound. In relevant situations, its guidance includes requirements relating to perimeter sealing and the acoustic performance or mass of doors, rather than prescribing a standard door thickness.
L – Energy Efficiency	Part L covers the thermal and energy performance of doors. It can set performance requirements for external doors, but it does not prescribe a standard door height, width or thickness.
M – Access to and Use of Buildings	Part M has the most direct impact on door dimensions. Approved Document M specifies minimum clear opening widths for certain entrances and internal doorways, as well as requirements relating to approach space and thresholds. The required clear opening depends on the type of dwelling and how the doorway is approached.
Q – Security in Dwellings	Part Q applies to new dwellings and requires reasonable provision to resist unauthorised access. Approved Document Q provides guidance on secure doorsets, including tested doorsets and an alternative specification for certain bespoke timber doorsets.

What are the Opening Requirements for Accessible Doors?

Approved Document M does not set one standard accessible door size. Instead, minimum clear opening widths vary depending on the type of dwelling and the doorway location.

For Category 1 visitable dwellings, the principal private entrance should provide a minimum clear opening of 775 mm, while internal doorways may require 750 mm, 775 mm or 800 mm depending on the corridor width and approach.

Category 2 and Category 3 dwellings have additional accessibility requirements, with Category 3 wheelchair-user dwellings generally requiring an 850 mm clear opening at the principal entrance and internal doors.

• Accessible entrance doors are commonly designed to provide an effective clear opening of around 850 mm, although the required effective clear opening depends on the building type, approach direction and applicable requirements.
• Accessible internal doors: 750 mm, 775 mm, or 800 mm (depending on the clear opening size, approach angle, and corridor width.)

Are Fire Doors a Standard Thickness?

Approved Document B sets fire-resistance requirements for fire doorsets in different situations, but it does not prescribe a standard door-leaf thickness. The thickness of a fire door can therefore vary depending on its construction, manufacturer and tested fire-resistance performance.

• Fire Resistance Rating FD30 - Typically 44 mm thick and provides 30 minutes of fire resistance (standard for residential and low-risk commercial spaces).
• Fire Resistance Rating FD60 - Approximately 54 mm thick and provides 60 minutes of fire resistance (because higher fire resistance ratings typically require additional insulating core materials).

Doors rated FD90, FD120, and FD240 vary considerably in thickness, depending on the tested doorset.

Important Note: Fire resistance relates to the performance of the complete doorset and its tested or assessed configuration, rather than door-leaf thickness alone.

How to Measure a Door

To measure for a made-to-measure door, you’ll need to record the width, height and thickness of your existing door or door opening. For the most accurate results, use a rigid metal tape measure and take each measurement in more than one place.

Because made-to-measure doors are manufactured to your exact requirements, it is important to provide precise measurements rather than simply choosing the closest standard size. This helps ensure the new door is built to fit your opening correctly.

Need more help with measuring your external doors? Go to our Advice Centre to see our door installation video tutorial.

Standard-Size vs Bespoke External Doors

Standard-size doors are often a practical option for internal doors, especially if you need a quick replacement or are working to a tighter budget. However, external doors usually benefit from a more tailored approach, as they need to fit securely, perform well and suit the style of your property.

A bespoke door can be particularly useful if you are:

• Restoring a period property.
• Replacing a door in a non-standard opening.
• Looking for a specific design, colour or configuration.
• Working with accessibility requirements.
• Ordering a complete external door set with a frame and threshold.

Our Minimum and Maximum External Door Sizes

At Modern UPVC Windows, we offer numerous door sizes that cover broad minimum and maximum measurements, including:

Door Type	Minimum Size (Width x Height)	Maximum Size (Width x Height)
UPVC Doors	700 mm x 1650 mm	3350 mm x 3200 mm (Top Light / Side Panels)
Full-Glass Flush	700 mm x 1970 mm	1050 mm x 3260 mm (Top Light)
French Doors	1000 mm x 1905 mm	3950 mm x 2900 mm (Top Light / Side Panels)
Flush French Doors	1000 mm x 2000 mm	1900 mm x 3260 mm (Top Light)
Sliding Patio Doors	1400 mm x 1000 mm (2 Panes)	6000 mm x 2390 mm (6 Panes)
Aluminium Bifolds	750 mm x 1900 mm (1 Pane)	6400 mm x 2559 mm (6 Panes)
GRP Composites	638 mm x 1985 mm	3322 mm x 3127 mm (Top Light / Side Panels)
Timber Composites	670 mm x 1984 mm	2650 mm x 3019 mm (Top Light / Side Panels)
Stable Doors	670 mm x 1931 mm	2650 mm x 3019 mm (Top Light / Side Panels)
Double Doors	1221 mm x 2039 mm	3541 mm x 3019 mm (Top Light / Side Panels)
Fire Doors (FD30)	670 mm x 1931 mm	1010 mm x 2126 mm

Made-to-Measure External Doors in the UK

Modern UPVC Windows manufactures and supplies made-to-measure external doors to trade customers and homeowners in the UK. Using our online design tool, you can design and visualise your new doors and instantly receive a quote. No forms or waiting.

Our premium doors and windows are made in our factory and backed by a price-match promise and 10-year guarantee. Not to mention, we offer installation services to customers across the Midlands, and expert aftercare support whenever you need it.

Whether you’re looking for a UPVC door, GRP composite door or fire door, you can explore our full product selection below. Each door can be made to measure and customised to suit your home, with options for colours, glazing, hardware and more.