On a list of things most often done wrong in tailored menswear, wearing a tie at an incorrect length would likely rank in the top 3. Fortunately, this is an easy problem to fix. Just as easily as a man can wear his tie at an incorrect length, he can also wear it at a correct length. So, ‘how long should I wear my tie?’ you may ask. Ideally, the tip of your tie should end in the middle of your belt buckle or waistband. For flat end ties, such as knit ties, it is best to have the tie end at the top part of your waistband.
When a tie is worn at the proper length it helps balance out your legs and torso, wearing a tie at an incorrect length can throw the balance of the ensemble off. When worn too long it can make the whole look look frumpy and sloppy. When worn too short the look can look clownish.
Keep in mind, you want to have the right length when you are standing at your normal posture. Not the super upright and straight backed posture you may use when checking yourself out in the mirror (it’s okay, we all do it, I’m guilty of doing it sometimes); but the posture you normally walk and stand with. Another thing to keep in mind is that the type of tie knot and width of the tie do not matter, the tie length should still remain the same. Which is to say that the tip of the tie should end near the middle of your belt buckle or waistband. Your height and weight also matter little, wherever the middle of your waistband is, is the proper place for your tie to end.
Given the correct length of the tie depends on the height of the waist of your pants the actual length you wear your tie may very. You will not always have your tie the same length. In short, the correct length to wear your tie is relative to your waistband.
Above you will see what is hopefully a helpful graphic that I put together. I hope it helps explain and show the correct tie length in an easy to understand manner.