Q:

How many days of internship am I allowed to do with a F1 visa (foreign PhD student in the US)?

I (French citizen) am doing a PhD in computer science in the US: over the course of my PhD, how many days of internship am I allowed to do? I have a F1 visa. I plan to do several internships and would like to know the maximum amount of time I can work as an intern. 

A:

There's no maximum amount of time you can work as an intern. As long as you're complying with the F1 requirements (including being in good standing with your school and various degree-related and course-work related requirements) - you can work as many days as you wish.
However, there's a difference between full-time and part-time internships. Part time (up to 20 hours/week) does not affect your OPT. Anything more than that comes from your OPT quota (which is up to a year, so if you have a year or more full time CPT - you lost your OPT).
Here's a detailed explanation on the CPT (foreign students' internship) program from UPenn. Your school probably has a similar page, or an international students' office where you can inquire.

