I'm really confused. I've only ever used metric in my life. Recently I'm trying to build a IOT device and there is plumbing and water involved.
I was looking for a 19mm fitting, but on Amazon and other sites it's always advertised in inches. John Guest 3/4" BSP x 1/4" Push Fit Tap Adapter
I did the conversion and 3/4 inch, according to my calculation, should be around 19mm. But whenever I order these fittings they always send me a larger size. The resulting size is always around 25mm when I measure it.
To me it seems like 3/4 inch doesn't actually mean 3 quarters of an inch?