On the topic of conversion, I have a free and simple to use conversion program on my computers. It makes math for old people like me really simple (read that as not necessary).
https://joshmadison.com/convert-for-windows/I have that on my computer and use it fairly frequently.
A number of years back, we were required to do some design work for the US Govt in metric. But in reality it was faux metric (they called it "nominal" metric), because they don't make things like plywood in other than English units. Pipe sizes were all actually English, but just referred to in a nearby rounded off metric, dimensions. Even in Europe and other metric nations, Pipe manufacturers produce in English sizes (which are actually "nominal" as well). Same with the guys doing sheet metal work. If you ask a tin-knocker for a 200 x 200 mm duct, he's going to give you an 8 x 8 inch duct.
A few years later, the Govt went back to English units.
