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In this part of our Metric Data series we are looking at standard door sizes.

You could say this post title “Standard Door Sizes” is a little misleading. Technically speaking there are no standard door sizes but rather most common sizes or most popular. Here we are going to look at the different size doors that are used the most.

The building regulations have standard clear width opening sizes for entrance doors in dwellings and buildings other than dwellings. Here we will be looking at doors associated with dwellings predominantly. The building regulations also have standards depending on whether a building is ‘visitable’, ‘adaptable & accessible’ or ‘wheelchair user’ – be sure to familiarise yourself with these different meanings and requirements by reviewing Approved Document Part M.

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Standard Door Sizes

Door sizes can be confusing due to the fact many doors are still manufactured in imperial sizes. Although metric sizes are becoming more common, there is often a mix of sizes just to keep us on our toes.

Standard External Door Sizes

External doors usually have a thickness of 44mm.

Standard external door sizes in metric

2000mm x 807mm
2040mm x 926mm
2040mm x 826mm

Building regulations state that an entrance door has a minimum clear opening width of 775mm in a visitable dwelling.

Building Regulations diagram – measurement of clear opening

To calculate clear opening, 60mm can be deducted from the door size to take into account hinges, door stop and thickness of the door.

An adaptable and accessible dwelling must have a clear entrance door width of 850mm.

A wheelchair user dwelling must also have a clear entrance door opening width of 850mm.

Standard external door sizes in imperial

1981mm x 838mm (6’6” x 2’9”)
1981mm x 762mm (2’6” x 6’6”)
2032mm x 813mm (6’8” x 2’8”)

Standard Internal Door Sizes

Internal door sizes can also vary widely. Generally, internal door thickness tends to be 35mm for a standard door, but can go up to 40mm. Fire doors will be 44mm for a half hour fire rating and 54mm for an hour fire rating.

Standard internal door sizes in metric

2040mm x 726mm
2040mm x 826mm
2040mm x 926mm
2000mm x 807mm

Standard internal door sizes in feet

1981mm x 686mm (6’6” x 2’3″)
1981mm x 838mm (6’6” x 2’9”)
1981mm x 762mm (2’6” x 6’6”)
2032mm x 813mm (6’8” x 2’8”)

Accessible internal door sizes

The building regulations state that internal doors must have a clear opening width of 750mm as a minimum when approached from a corridor of 900mm from head on. This increased to 775mm clear opening width when approach is not head on, from a corridor of 1050mm. Door width must have a clear opening of 800mm from a 900mm corridor when approach is not head on. This applies to Part M4(1) and M4(2) visitable dwellings and accessible and adaptable dwellings.

Building Regulations table showing clear opening widths of internal doors for accessible dwellings

An 826mm door leaf, up to 44mm thick will be deemed to satisfy the clear opening width requirement of 775mm.

A wheelchair user dwelling (M4(3)) must have all internal doors clear opening width of 850mm as standard.

Fire door sizes

All standard door sizes tend to be available as fire doors, with an increased thickness of 44mm or 54mm, for a half hour rating (FD30) or hour rating (FD60) respectively. It is also necessary to ensure your ironmongery, frames, and intumescent seals also adhere to the building regulations for fire doors.

Other doors

French door sizes

French doors are double leaf doors, that tend to open out, available in both hardwood, softwood and of course UPVC. Typical sizes for french doors include: