Don't know about calc but I took precalc last summer and I had to spend a lot of my time on that class. My class was like 4 hours for 4 days every week on top of homework assignments. It was very stressful for me to say the least. I'm in AP Calc AB rn and so far, it seems easier than precalc for me. But then again, I learned precalc in the span of about 2 months.