Close the door and look at the gap. That's the only measurement that actually matters, and it's the one most people skip before ordering a draught excluder that's either too short to cover the width or so long it bunches up at the ends.
Measure the width first
Run a tape measure along the bottom of the closed door, edge to edge, at floor level. Write down the number in centimetres. That's it — that's the measurement that decides which excluder fits.
Most UK doors fall into a small number of standard widths, so if you don't have a tape measure to hand, these are the common ones:
- Standard internal door: 762mm (30 inches)
- Standard external front door: 838mm (33 inches)
- Older or narrower internal doors: 686mm (27 inches)
- Wider or replacement front doors: 914mm (36 inches)
These are guides, not guarantees — especially in older houses, where doors have sometimes been planed down or replaced with whatever fit at the time. Measure if you can.
Round up, not down
A door snake that's slightly longer than the gap sits fine — it just curls a little at one end. One that's too short leaves a visible cold strip at the edge, which rather defeats the point. If you're between two sizes, take the longer one.
Fixed versus adjustable
A fixed-length excluder is cheaper and works well if you know the exact width and it isn't likely to change. An adjustable excluder is worth the extra couple of pounds in an older house, where no two doors are quite the same, or if you want to move it between rooms as the year goes on — kitchen door in the evening, front door overnight.
Windows work the same way
The same rule applies to a draughty window sill: measure the width of the sill or the bottom of the window frame, and size the excluder to sit along the whole length rather than leaving gaps at either end.
Once you've got the number, the rest is easy. Have a look at what we stock — weighted door snakes, adjustable strips, and the kind that clips to the bottom of the door itself, all sized for the doors British houses actually have.