How long can I stay in the U.S. as a tourist?

Your I-94 record shows your allowed stay so check it online.

You can ask for an extension using Form I-539 before your time is up.

If you are on a Visa Waiver ESTA, you can only stay 90 days.

The officer at the airport decides how long you can stay and if you stay past your allowed time, you may be banned from coming back.