If I'm interested in going to grad school to do theoretical physics how much math am I expected to pick up as an undergrad? I know theory requires a lot more math than experiment but how much more and do I need to do it while I'm still an undergrad or will I be able to pick it up along the way while I'm in grad school. I wish I had time to take more math courses but I didn't take my first physics course until my sophomore year of college so now I'm trying to cram all my physics courses into 3 years which gives me little room to take extra math courses. The courses I'll have for sure by the time I graduate are vector calculus, linear algebra, and differential equations. I might have room to take like 2 more math courses but probably not more than that. Which do you think would be the most useful? And do I have any realistic shot at getting into a good grad school and doing theory with my limited background in math?