Anything can be self-taught if you apply the effort.
For Calculus, you would need to develop numerous tricks to easily solve a certain problem, and you would also have to find a way to easily memorize formulas, rules, and whatnot.
Can calculus be self-studied?
Absolutely! I self-taught a lot of subjects when I moved from the UK to the US - mostly done by reading and re-reading a lot of boring books. It doesn't have to be that way though, my aunt uses this to help my homeschooled cousin and she says it's pretty innovative and works really well - check it out here.