Typically up to 6 months per visit, but the officer decides at entry.

You can request an extension, but apply before your stay expires.

Don’t overstay, it could affect future visa applications.

On a B-2 tourist visa, you can stay in the U.S. for up to 6 months per visit, as determined by the Customs and Border Protection officer at entry. You may be granted less time, depending on your circumstances. But how long you have to stay is always on your I-94 form. so please double check that.