At some point in your wanderings through the trecherous pathways of the interweb you must have come accross this old chestnut “Why are wands measured in inches if Hogwarts is in Britain.” Then below it are comments from 20,000 angry English people.
So let me address the question once and for all. This is a 30cm rular of the type found in schools all over the country.
And what’s that on the other side? Oh it’s inches because we use both. Britain uses a bit of a mix of metric and imperial. Road signs are in miles, I am 5′ 4″ tall and weigh 8 stone. If I’m making a cake I prefer to use pounds and oz. Therefore it is not surprisung that wands would be measured in inches. Part of the reason wand jokes are so popular, I’m sure, is because penises are one of those things always measured in inches. If you also consider that wizards are not exactly up on what is happening in the muggle world it seems extremely likely that they might use wholly imperial measurements. But generally speaking most British people are perfectly at home with feet and inches thank you very much. America does not have some special ability to understand non metric measurements.