¿Cómo dices esto en Inglés (US)? Is "What's up" same as "How are you"? and how to respond if people say "what's up"?

See a translation

It can be the same! Usually, you use "what's up" with friends or close family, and "how are you" with strangers, teachers, bosses, etc. If someone asks "what's up" you can say "not much" or you can say what you are actually doing, like "I'm doing homework." Also, you can just say "what's up" back to them, like saying hello!

Example:
Friend: "what's up?"
You: "I'm with my parents"

Friend: "what's up?"
You: "not much, you?"

Friend: "what's up?"
You: "what's up."

Also, you usually say the same greeting that someone greeted you with! So, if a friend does say "how are you" you should answer with "I'm well" or something like that, because saying "what's up" then sounds strange.

Friend: "how are you?"
You: "I'm tired. How about you?"

I hope this helped!! :)