When applying for a job they say you should wait ~2 weeks after the interview for a response and if you havent heard anything presume you havent got it. Is the same true for a PhD? One supervisor said they would let me know the outcome by Thursday (that was 2 weeks ago)? Is it okay to e-mail supervisors to find out the outcome? How long after the interview should you wait?

What DanB said

hey,

It depends on how many candidates they have. You could have been the first to be interviewed.
I waited 5 weeks to get a rejection.
I think it's not fair saying they would give you the reply and then don't give it to you for another two weeks. They either can't be bothered to inform you you didn't make it or have serious trouble to decide between you and someone else (fingers crossed it is the second).

I hope you make it and it goes well.
I am waiting for two replies as well, one of them is just my dream project with perfect team and perfect department and perfect location and everything and I am just too scared to ask them about the outcome.

Good luck:)