Reply
Most mailorder or online shops have a measure>size chart to give you an indication of what you need.
Just have a look there!
No general rule as there are too many different size systems.
Will be a trial-and-error thing in the beginning!
If you’re shopping in a TG-friendly shop, on the other hand, you just ask and try! And don’t be too scared.
Most shops just want to sell stuff. Rest is none of their business!!