Calculus is the very most basic of all college-level pure and applied math. An affinity for calculus doesn’t necessarily indicate any aptitude or affinity for real theoretical math. I read this thread to my boyfriend, who majored in math and is now a PhD student in math, and he found it laughable that you think a Fields Medal would be “pretty sweet”. Get a couple of undergrad years under your belt and see where you are. The thing about getting a PhD is that you don’t “break even” on lost work experience and wages for a very long time. My PhD stipend at one of the best-funded programs in the country is a little over $30,000/year. A friend who graduated with the same credentials as me is making about $80,000 right out of college, so over a 5 year program I’m behind by $250,000. My boyfriend’s stipend is even less than mine. So it makes no sense financially to want a PhD. Find a subject you’re passionate about at the college level, and look beyond prizes and money. And figure out what a PhD student and a researcher with a PhD actually does with their time. If you don’t like that you don’t belong in the academic world.