457 × 1981 mm door
457 × 1981 mm
18 × 78 in · 1′ 6″ × 6′ 6″ · United Kingdom · an exact inch size in millimetres
What this door is for
The narrowest standard British door, 1 ft 6 in wide. Used for cupboards, airing cupboards and meter boxes rather than rooms — it is too narrow for a person carrying anything.
Three measurements, not one
A door has a leaf size, a rough opening and a clear width, and they are all different. Ordering against the wrong one is the usual way a door arrives that does not fit.
| Millimetres | Inches | What it is | |
|---|---|---|---|
| Leaf | 457 × 1981 | 18 × 78 | The door itself — what you order |
| Rough opening | 557 × 2041 | 21.9 × 80.4 | The hole in the wall, allowing for frame and shimming |
| Clear width | 412 | 16.2 | What you can actually walk through with the door open |
The clear width is the one that matters for getting furniture through and the one accessibility rules are written against — a 18-inch door does not give a 18-inch opening, because the leaf thickness and the stop remain in the way.
Other United Kingdom sizes
| Door | Leaf | Rough opening | Clear width |
|---|---|---|---|
| 533 × 1981 mm | 533 × 1981 mm | 633 × 2041 mm | 488 mm |
Frequently asked questions
What is the rough opening for a 457 × 1981 mm door?
About 557 × 2041 mm (21.9 × 80.4 in). The opening has to take the leaf, the frame on both sides and enough slack to plumb it — roughly 50 mm each side and 60 mm above. Never order a door against the size of the hole.
How wide is the actual opening once the door is open?
About 412 mm of clear width. The leaf swings back but its thickness and the door stop stay in the way, so roughly 45 mm is lost. This is the figure accessibility rules are written against, not the door width.
What is a 457 × 1981 mm door used for?
The narrowest standard British door, 1 ft 6 in wide. Used for cupboards, airing cupboards and meter boxes rather than rooms — it is too narrow for a person carrying anything.
Why is 457 mm such an odd number?
Because it is not a metric size. 457 mm is exactly 18 inches, or 1′ 6″ — a British door size from before metrication, converted rather than redesigned. The same goes for the 1981 mm height, which is exactly 78 inches.