Generally, you want the tv in the same place as your eyes from wherever you plan to watch it. If you have a couch across the room, sit down and see where your eyes naturally land in the area where you want your tv. That’s the height you want.

@[email protected] has good advice. Generally, this is what is acceptable:

• if placed above a fireplace, it's too high
• if TV has to be angled down, it's too high
• if you are standing and tv is at eye level, it's too high

This tom's guide is a decent start: https://www.tomsguide.com/us/how-to-mount-tv,news-24719.html