Doors are generally produced in a range of popular and standard sizes. The actual range of standard sizes available will depend on the manufacturer and the style of door. If you need a door which isn't a standard size you will need to find out if your choice of door can be trimmed or made to custom sizes. There will be a limit to how much can be trimmed from any door, if any can at all, and custom made doors will be more expensive.
External doors are often sold pre-hung as a complete door set
, so they have an appropriate frame which matches the properties of the door slab/panel itself. If you want to keep an existing frame you can also get door slabs without a frame. The standard sizes of door sets are the dimensions of the frame which will be installed in the rough opening. The rough opening will usually be 5-10 mm larger than the frame to allow for movement and straightening of the frame. This gap can then be filled with an insulating sealant.
The size of the door panels you'll need for a double French door or a multi-leaf patio door will need to be worked out in relation to the dimensions of the opening and how many leaves the configuration will use. If you want sidelight or fanlight panels, you'll also need to consider their dimensions as they need to be included in the door frame's measurements.
The standard heights and widths of external doors are often comparable to standard internal door sizes. The main difference is seen in the thickness of external doors. As external doors need to be more sturdy they are usually thicker, with 44mm (1 3/4") being the most common thickness in domestic settings. External doors that are 54mm (2 1/8"), or thicker, and 40 mm (1 2/3") are sometimes also available.
Popular external door sizes
If you are keeping an existing frame, and just replacing the door itself, then you will need to get the measurements only for the door panel, this can also be called a door leaf or a door slab, when replacing the frame as well you will want to ensure that you calculate measurements for a doorset - which will mean working out the rough opening size and the external measurements of the frame and then get a door panel to fit that frame.
Popular external door panel heights
Metric (mm)
Imperial (inches)
1981 mm
78"
2032 mm
80'"
2083 mm
82"
2134 mm
84"
Popular external door panel widths
Metric (mm)
Imperial (inches)
686 mm
27"
762 mm
30"
813 mm
32"
838 mm
33"
864 mm
34"
915 mm
36"
Popular external doorset sizes
External doorset frames and door panels are the easiest way to replace an entire door frame and panel as they are pre-finished and come ready to be assembled easily and will fit into your rough opening.
If you are unsure about any measurements you should consult a local bulding professional.
Popular external doorset heights
Metric (mm)
Imperial (inches)
2067 mm
81"
2118 mm
83"
2168 mm
85"
2220 mm
87"
Popular external doorset widths
Metric (mm)
Imperial (inches)
850 mm
33"
901 mm
35"
926 mm
36"
952 mm
37"
1003 mm
39"
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