Does a C in Calculus disqualify me off the bat?

A lot of firms don't ask to see your transcript until after they've already given you an offer. If you have a good GPA, that's what matters. To the extent that it does matter, networking can easily overcome it. That said, the semester isn't over yet so go all out to get 100's on everything else in that class, if you can.

One grade won't make or break you, just don't let it become a habit

I agree with Newspeak. Many things can be overcome with effective networking. I had a very mediocre SAT score (1900), but was still able to secure an offer from one of the "elite boutiques".

One thing that can't easily be overcome, however, is a low GPA. So do whatever it takes to keep it above 3.5 and you should be fine.

DollaDollaBillI'm a sophomore at a top school and I've had a difficult semester (personal issues). Most likely, I will end up getting a C in Calculus. It is my lowest grade in college so far and an outlier in terms of what I've normally been getting. Will top consulting firms see this and pass me up off the bat, even with an otherwise respectable GPA (that I will continue to improve) and solid leadership and extracurricular experience?

Don't worry, if consulting doesn't work out, you can still easily get a job as a UBS quant.

not a big deal at all.

No, but not recycling does.

Pack your shit. Mexico might be your only resort.

I got an F in calculus my freshman year and still landed plenty of interviews with BBs. All that it matters for is to lower your GPA, which obviously is a concern, but not any more than if it had happened in any other class.