SEAS offers undergraduate and graduate courses in Computer Science. SEAS faculty also offer several Freshman Seminars. Many additional courses of interest to concentrators can be found in the Applied Mathematics, Engineering Sciences, Mathematics, Physics, and Statistics sections of the my.harvard course catalog.

The SEAS 4 year course plan contains the most up to date plan for courses to be offered in the near future. You can filter the “catalog” entry to CS to see only Computer Science courses.


Most students start with CS50, even if they have had an AP course in Computer Science. The course is designed to accommodate both students who are starting from scratch and students with prior programming experience. However, some students have sufficient programming background to skip CS50 and start with CS51 or CS61. See the CS50 FAQs for more advice, or consult the Director of Undergraduate Studies.

Students should consult with the Mathematics Department, Chemistry Department, and Physics Department for advice about appropriate placement in courses in those departments.

CS20, Discrete Mathematics for Computer Science, teaches the mathematics needed for later computer science courses that is not covered in the calculus and linear algebra sequence in Mathematics and Applied Mathematics. Many students will not need to take CS20, but students with no background in writing mathematical proofs should consider taking this course. The CS121 page on Background and Prerequisites is a good source for figuring out if you need to take CS 20 before taking courses such as CS 121 and CS 124.

Which courses count for what?

The official information is in the handbook entry but we summarize here which courses count for fulfilling various requirements. The list below is not exhaustive, and if there is any conflict between this list and the handbook, the handbook information is the correct one. We generally allow a student to replace a course with a more advanced course of the same type, though you should ask us for authorization in advance for each such case.

Harvard extension school courses do not count for CS concentration courses. Harvard summer courses could potentially count if they are equivalent to courses that are counted in the concentration (e.g., summer versions of CS 50 or Stat 110 or other math classes). Courses taken at other universities do not count towards the concentration, unless part of an official study abroad program, or you are a transfer student. (If you are a transfer student, come talks to us and we will make the decision on which courses to count on a case-by-case basis).

With the exception of CS 50 (which may be taken SAT/UNSAT, though not Pass/Fail), all courses for either fulfilling either the CS concentration or secondary requirement must be taken for a letter grade.

  • Mathematical background: The Linear Algebra requirement can be fulfilled by one of Math 21b/22b/23a/25a/55a or AM 21b. The statistics/probability requirement can be fulfilled by STAT 110. The calculus requirement can be fulfilled by one of Math 21a/22a/23b/23c/25b/55b or AM 21a. (Note that you don’t need to take both a statistics/probability course and a calculus course; if you do then you can count STAT 110 as a technical elective.)

  • Theory requirement: The standard and recommended way to fulfill the theory requirement is to take CS 121 and CS 124. However, other CS 12x courses can replace CS 124, and AM 107 also counts as a theory course at the moment. (Note: As of fall 2018, AM 106 will no longer satisfy the theory requirement.) Replacing CS 121 requires a course with a significant computational complexity requirement such as CS 221.

  • Technical Electives:

    • Harvard CS courses: The following Harvard Computer Science courses count as technical electives: (1) every CS 1xx or CS 2xx course, (2) CS 20, (3) CS 91r (only one semester) and CS 96, (4) If you took CS 50 + CS 51 + CS 61 then one of CS 51 or CS 61 can count. If a course is cross listed as both a computer science course and a course in another department then it counts even if you took the course under its other number (e.g., STAT 121a or AC 209a is considered the same as CS109a).

    • Other Harvard courses: The following Harvard courses count as technical electives: STAT 110, STAT 195, Math 154, AM 106/107/120/121/207, ES 50/52/54/153/170, Physics 123.

    • Summer courses: Procided you get college credit for it, CSCI S-111 counts as equivalent to CS 50,

    • Other courses: Many MIT course 6 courses can be used as technical electives: consult the DUS before enrolling. In particular, Harvard students have taken MIT courses 6.036, 6.042, 6.046, 6.045, 18.404 / 6.840, 6.841, and 6.806 in the past. Note that MIT 6.006 (“Introduction to Algorithms”) does not count for the CS concentration (MIT 6.046, “Design and Analysis of Algorithms”, does count). Some study abroad courses count, though you should always check with the DUS’s in advance. Courses and requirements change, and you should not assume that a course will count even if you know it did so in the past.

  • Breadth requirement: A technical elective can count towards the breadth requirement if it is a CS course and its penultimate digit is between 3 and 8. Courses such as CS 10x or CS 19x do not count towards the breadth requirement. Non Harvard CS courses: Physics 123/Engineering Sciences 153 is considered equivalent to a CS course with penultimate digit 4. AM 207 is considered equivalent to a CS course with penultimate digit 8. Some MIT or study abroad courses might count for the breadth requirement on a case-by-case basis.

  • Secondary: The requirements for a CS secondary are rather light (only four courses) but these have to be Harvard CS courses numbered 100 and higher, or CS 50/51/61. You cannot count non-CS Harvard courses, MIT courses, nor study abroad courses. The one exception is that if a course is cross listed as both a computer science course and a course in another department then it counts even if you took the course under its other number. See here for more information. If you are a transfer student, contact the CS DUS’s for information on whether courses from the previous institution can count.

Table of course substitutions for concentration

The following table summarizes some course substitutions that are allowed. Courses change, and so can the allowed substitutions - always check with the DUS’s for updates. Note that these substitutions are only valid for the computer science concentration and not for a CS secondary.

Course(s) Can be used in place of
Math 22a, 23b,23c, 25b, 55b, 110, 112, 113, 114, 115, 116, AM 105, 108, and 111 Math 21a: Multivariate Calculus
Math 22b,23a,25a,55a,121,122, AM 120,121 Math 21b: Linear algebra
STAT 210 STAT 110: Probability
STAT 111 STAT 110: Probability
STAT 129a/b , AC 209a/b CS 109a/b: Introduction to Data Science
CS 221 CS 121: Introduction for Theoretical Computer Science
CSCI S-111 (Summer course intro to programming) CS 50
STAT S-110 (Summer course: intro to probability) STAT 110: Probability
CSCI S-109A (Summer course: intro to data science) CS 109a
MIT 6.00 CS 50
MIT 6.042 CS 20
MIT 6.046 (not MIT 6.006!) CS 124
MIT 6.045, MIT 6.840 CS 121: Introduction for Theoretical Computer Science
MIT 6.849: Computational Geometry CS 12x
MIT 6.841 CS 221
MIT 6.034 CS 182
MIT 6.806, MIT 9.19 CS 187
MIT 6.036 CS 18x (check with instructor before taking CS 181)
AM 207 CS 28x
EX 1034 CS 13x
PHY123, ES153 CS 14x
CS 1xx, 2xx Tech elective, breadth if penultimate digit 3-8
CS 20 Tech elective (no breadth)
CS 91r Tech elective (one semester only)
CS 96 Tech elective (no breadth)
CS 51 / CS 61 One of CS51/61 can satisfy breadth if student took CS50+51+61
AM 107 Tech elective (no breadth), also second theory course
AM 106 Tech elective (no breadth): as of fall 2018 cannot be used as second theory course
AM 120,121 Tech elective (no breadth)
STAT 110 Tech elective (if not used for probability requirement)
STAT 121, 195 Tech elective (no breadth)
Math 154 Tech elective (no breadth)
ES 170 Tech elective (no breadth)
MIT 6.006 Can not be used for concentration requirements
Math 157 Can not be used for concentration requirements
CS 1 Can not be used for concentration requirements
CS 90ncr Can not be used for concentration requirements