Eh, you can estimate and be relatively close. I used PaycheckCity once I got my salary offer, but before I had gotten my first paycheck, and it was a pretty close estimate to what I actually paid in both federal and state taxes (but caveat is also that WA has no state income tax). I used a similar calculator when I lived in NYC, which has a much more complicated tax code, and still got a relatively close estimate. Someone making $60K would probably take home around $4,000 a month, give or take - but that’s the roughest estimate.
If you’re trying to figure out how much to borrow, the general advice I’ve heard is that you shouldn’t borrow more than you expect to make in your first year out of college. However, I am kind of at odds with that advice, because it’s difficult to predict what you’re going to make in your first year out of college - you may change your major, decide to work for a nonprofit, have a difficult time finding a job in your field, do TFA, whatever. Generally speaking, the federal Direct loan limit about (which I think is around $30K) is the recommended max a student should borrow for college.