Student Visa USA
 

How long does it take to get a student visa, when you are in possesion of a I-20 form ? How long does the visa let you stay in the usa ?

You have to wait for a interview appointment at the US embassy, which may take a few weeks or even months, go in to be interviewed, and then the visa will be mailed within a few days. F-1 visas are almost always valid for 5 years and multiple entries, if you are citizen of a EU country. Your actual length of stay, however, is determined by the end date of your I-20 and/or the duration determined by the immigration officer upon arrival.

In which country are you?
You need to make an appointment at the US Embassy in your own country (this a very variable, it could take 2-12 weeks). If your papers are fine you get your visa soon (few days).

Check the Visa appointment website. It gives the current average wait times for most US consulates for you to get your appointment. How to make the appointment and how soon you will get your visa depend on the actual consulate. Check the list of US consulates to find the one closest to you.