Completely agree with @ucbalumnus.
Things will happen and come up all of the time which impact your graduation dates. Plus, you intend to double major. Each major has its own graduation requirements. English is labor-intensive with multitudes of written assignments.
If you plan on a Ph.D. in math, you may be required to complete a dissertation. This takes up a lot of time. Some schools require research, hence the Ph.D.
Davis appears to require both:
https://www.math.ucdavis.edu/grad/gpc/degree_req/math-phd-requirements-starting-fall-2021
- Summary - 24 units of core coursework, and 24 units of electives are required for a total of 48 units. Full-time students must enroll for 12 units per quarter including research, academic and seminar units. Courses that fulfill any of the program course requirements may not be taken S/U unless the course is normally graded S/U. Once course unit requirements are completed, students can take additional classes as needed while completing their dissertation, although the 12 units per quarter are generally fulfilled with a research class (299) and perhaps seminars. Per UC regulations students should not ordinarily enroll in more than 12 units of graduate level courses (200) or more than 16 units of combined undergraduate and graduate level (100, 200, 300) courses per quarter.
Teaching Skills
The department has a commitment to develop outstanding teaching skills in its Ph.D. students. All Ph.D. students are required to be teaching assistants for at least one quarter. Exceptions require approval of the Graduate Program Committee. Students beyond their first year are encouraged to apply for positions as Associates In mathematics to develop and improve their lecturing skills. The department makes every effort to give all students exhibiting solid teaching skills the opportunity to serve at least one quarter as an Associate In mathematics.
Law School will take time and money. I hope you are able to fund all of your studies because, it will be very expensive.