In essence, a tie is an odd thing. It is a piece of fabric around one's neck that has no practical purpose — and gets a bit uncomfortable when worn for a whole day.
But in several cultures, wearing a tie can have various connotations: signalling style, professionalism, being in control — or having lost it, depending on the style of the tie. Exactly what you signal depends to a large extent on the width of the tie as measured at its widest point.
In fashion, 4-6 cm
Trends change all the time, but the skinny tie — that has at times been considered a little 'progressive' — is currently in style. 6 cm would be considered moderately skinny while 5 cm is "standard hipster skinny". 4 is extreme while still retaining the shape of a tie.
Business, 6-8 cm
A rule of thumb if you are after a classic business style, is that the tie should be as wide as the lapel of the suit you are wearing it with. It's that simple. This often translates to 6-8 cm — current slim fit suits have lapels at the lower end of this spectrum.
Classic, 7 cm
Of course, you can wear a tie without a suit and still be after a classic style. Or just want to have a nice all-rounder at hand. In that case, 7 cm is a pretty safe bet. A "neutral" tie.
Old-fashioned, 8-10 cm
If you like wearing non-slim fitting suits and/or you are well built, a wider tie could work well. Generally, wider ties need to be subdued in both colour and pattern so as not to become too dominant. A wide tie tends to be perceived as less "slick", or a bit old-fashioned.
Retro, 10+ cm
Anything above 10cm will appear as if it was snatched from the 1970s. If you are going to a costume party, or just making a statement, 10+ is for you.