Visas with a grace period are:
- F-1, 60 days.
- J-1, 30 days.
- M-1, 30 days.
For all other visas, if you have not applied for an extension, you are expected to leave on the earliest of either the expiration of your I-94, or the point where you fall out of status. For work visas, you would fall out of status when your employment ends.
If you timely filed for an extension of the visa, you are allowed to remain in the US until USCIS makes a decision on the application. If the application is denied, you are expected to then leave.
The longer you stay in the US out of status, the harder it will be for you to come back to the US, and if you accumulate 180 days or more out of unlawful presence in the US, you will be barred for three or ten years from the US after you leave.