Our view is that the width of a tie should match a man's height and weight with fashion being an afterthought...
Why? Because our focus is on making beautiful ties that you can wear for many years and not be concerned with fashion. Matching to a suit's lapel is a sartorial myth and not an issue.
In America men tend to have bigger bodies as time goes on and 3.5 to 3.75 inches is a classic width for a tie at its widest. If you are young, or very fit or naturally slim then the width can be narrower. Keep in mind that there are local cultural differences, and men that go out at night to clubs often prefer narrower ties such as 2.5 inches.
As a practical matter the small end of a tie should be about two inches above the big end of a tie when tied. The reason for this is that we plan the taper of your tie to have a good sized knot and where you tie your tie influences your knot size. When your tie is too short your knot will tend to be smaller. To get your correct length measure the length of a sample tie very carefully, then tie your tie with the knot that you prefer. The big end typically will be in the middle of your belt. If there is a two inch gap between the big and small end you are all set, use the length of the sample tie. If not add or subtract as needed. Example the small end is four inches above the big end - add two inches to your tie length.
Very rarely men will ask for us to plan for both ends being the same length after tying your tie. In Europe there are more men wearing their ties this way than in America or Australia or Canada. The look is basically the same as a tie with a two inch length difference but it takes an extra minute sometimes to tie it correctly.
Having the small end be longer than the big end is very rare and not suggested for classic office wear...
A tie's length is also influenced by your knot type: All things being equal a half-Windsor needs two more inches than a four-in-hand knot and a full Windsor needs three more inches than a four-in-hand knot. This is due to the extra looping needed.