Denying offer of admission from graduate school after accepting The university that gave me an offer only gave me two weeks to accept the offer. I asked them for an extension, and they only gave me a week more. I have still yet to hear from the other universities I applied to; since it is only mid March. I am quite confused as to what I should do, I don't want to give back the offer after accepting it. But I also can't predict what the other universities decisions would be and neither am I too confident as to reject the one offer I do have. Would appreciate some advice. I applied to Masters program in Physics, in Canada.
Presumably the school you heard from was not your first choice. 

I'd just be as upfront as possible, with everyone. Next step is probably to contact the schools and/or professors you haven't heard from, say that you have another offer, and ask if they can give an update on the timing of their decisions. 

Depending on what those schools say, contact the school you were accepted to and request another extension until the specific dates that the other schools gave you.