Panel size charts are the right place to start when specifying a wall switch, because the three common formats really do map to regions: 86 by 86 mm across Europe and much of Asia, 118 by 76 mm in North America, and the larger 147 by 86 mm plate used across Pakistan and parts of the Middle East. Choose the wrong one and nothing fits. Choose the right one and you can still end up with a plate that will not go on the wall, because the two dimensions on the chart are not the ones that decide it.
Depth is the dimension nobody measures
A smart switch is a mechanical switch plus a radio module, a relay and usually a power supply, all behind the same face. That assembly is deeper than the mechanism it replaces, and it has to share the box with the conductors, which do not compress.
A shallow box that happily hosted a mechanical switch for thirty years may simply not have room. This is the most common reason an otherwise correct order ends up back in the van, and it is invisible from the front of the plate.
Fixing centres decide whether the plate reaches the wall
The second number is the distance between the mounting holes, and it is not derivable from the plate size. The 86 format uses a 60 mm centre; the larger formats use their own. If the box in the wall has lugs at a different spacing, the plate cannot be screwed to it no matter how close the outline looks.
This matters most in retrofit. New work follows the local standard, but anything installed decades ago, or anything from a different market that arrived with a previous owner, may not.
Cover matters when you are replacing, not building
The third consideration is not in any chart: whether the new plate covers the mark the old one left. A slightly larger faceplate hides paint lines, dust shadows and the small chips around the old screw holes. A plate the same size as the one you removed will show every one of them, and on a freshly decorated wall that is the difference between a job that looks finished and one that looks like a repair.
For replacements, going one size up in faceplate — while keeping the box fit correct — is often the cheapest way to an invisible result.
How to specify without a site visit
If you are ordering for a market you cannot visit, ask for three measurements from an actual installation rather than a catalogue: the internal depth of the box, the fixing centre distance, and the size of the opening the plate has to cover. Those three, plus the regional format, cover nearly every failure.
XingLiao builds wall switches in 86, 118 and 147 formats for different markets, made in Shenzhen alongside the wider smart switch range.
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