How to Apply to Biology at Caltech: No Major on the Application, a Shared First-Year Core, Then Declare the Biology Option at the End of the First Year, with Molecular and Cell Biology, Genetics, Development, Neuroscience and Undergraduate Research, and the Path for Domestic, International (Including Chinese) and Transfer Applicants

The California Institute of Technology (Caltech) calls majors “options”. Biology (Bi) sits in the Division of Biology and Biological Engineering (the catalog’s wording). Caltech has six academic divisions, and every undergraduate takes a core that spans them. The notes below follow Caltech’s website and are split into domestic students, international students (with a section for applicants from China) and transfer students. Chemistry, physics, mathematics and other majors are not covered here.

1. Biology options and related programs

• Biology option (Bi): listed on the admissions site’s majors list and in the catalog. The catalog says the option builds on a foundation in mathematics and the physical sciences, introduces the basic facts, concepts, problems and methods of biological science, and serves as a basis for graduate study in any field of biology or for admission to the study of medicine; coursework emphasizes the general and fundamental properties of living organisms and areas of current research rather than the traditional separate fields, and the division believes research participation should be part of each student’s program.
• Biology minor: Bi 8 and Bi 9; any two of Bi 122, Bi 117, NB/Bi/CNS 150 and Ch 41 a; and 36 units of advanced biology electives not used for the major; the transcript will read “minor in biology”.
• Related options on the majors list: Bioengineering, Computation and Neural Systems and the minor-only Neurobiology also appear; their requirements are not covered here, and biochemistry is a track inside the chemistry option (see the chemistry catalog page). The pages read show no separate undergraduate options in molecular biology, genetics, marine biology or ecology and conservation; such topics sit within the biology option’s courses, and no separate tracks are published.
• Degree type: the transfer page says Caltech awards the Bachelor of Science; the pages read do not mention a BA or other accreditation; not published there, so check the website.
• Premedical program: the catalog has a Premedical Program section saying the undergraduate course for premedical students is essentially the same as for biology students and has been generally accepted by medical schools, and it advises students contemplating medical school to consult the premed adviser at Careers, Advising, and Experiential Learning or a professor in the division. Medicine (MBBS/MD), nursing, pharmacy, dentistry, veterinary medicine and public health are outside the scope of this article; see the website.
• Outcomes: the pages read print no graduate-destination or employment data for biology; not published there. The catalog says only that the option is a basis for graduate study in biology or medicine.

2. Requirements of the biology option (catalog, 2026-2027)

• Required courses: Bi 8, Bi 9, Bi 117 (developmental biology), Bi 122 (genetics), NB/Bi/CNS 150 (introduction to neuroscience), Ch 41 abc (organic chemistry); Ma 2, Ma 3 and any two terms of Ph 2 abc (BE/Bi 25 may replace Ph 2 c, and the option representative can approve “reasonable” replacements). These are taken for letter grades, except Bi 8 as a first-year student, who must maintain shadow grades showing satisfactory progress.
• Laboratory or thesis: one advanced laboratory course (100 or 200 level), or Bi 21 with a presentation, or three terms of undergraduate thesis (Bi 90 abc).
• Biochemistry group: two courses from Ch/Bi 110 a, 110 b, 111, BMB/Bi/Ch 170, 173 or Ch/Bi 145.
• Scientific writing: Bi/BE 24 (6 units), or an equivalent such as En/Wr 84 plus an oral presentation at SURF Seminar Day, with option-representative approval.
• Electives: at least 8 biology electives, which must be biology or bioengineering courses at the 100 level or above; at least two must be 9 units and taken for grades, and at least four in total for grades. Bi 22 (undergraduate research) beyond a 12-unit minimum can count among the electives, and relevant courses from other options can be used with permission.
• Units: at least 170 units of biology must be taken and passed (any Bi 1 course, Bi 2, Bi 10 and BE/Bi/CNS/NB 197 do not count); the Institute total is 486 units.
• Scheduling: students arriving with a strong foundation may take Bi 8 and Bi 9 in the first year to open the widest range of electives, though these courses are designed for the sophomore year; Bi 10 or Bi 1x is not required but is commonly taken to meet the Institute introductory-laboratory requirement; prerequisites are advisory and can be waived by the instructor; BE/Bi 25 is strongly recommended for those aiming at graduate work in biology; undergraduates are generally welcome in 200-level courses with permission or strong preparation.
• Research: students may elect an undergraduate thesis (Bi 90); research can be arranged with individual faculty members or through the biology undergraduate student adviser; individual research uses Bi 22 and tutorial instruction Bi 23.
• Grade condition: the biology option catalog page read does not state a grade-point condition for staying in the option; not published there, so ask the division.

3. How admission works: the Institute first, an option at the end of the first year

• You do not choose biology on the application: the admissions site says every new student takes the same classes in the first two terms and declares a major (option) at the end of the first year; the application-requirements page does not ask for a major. You apply to the Institute, and the admissions office makes the decision centrally.
• Capacity and conditions: the pages read do not say whether the biology option has a cap or what it takes to move in from another option; not published there, so ask the division.
• Research: the admissions site says more than 90% of undergraduates do research and about half get involved in their first year; fellowships such as the Summer Undergraduate Research Fellowship (SURF) support it.

4. Preparation

• High-school courses (admissions site and catalog agree): four years of math including one year of calculus, one year of physics, one year of chemistry, one year of biology (recommended, not required), four years of English, and two years of history and/or social science (three or more recommended). A student who has exhausted the high-school math curriculum may have fewer than four years.
• If your school does not offer a course: if calculus, chemistry or physics is unavailable or there is an unresolvable course conflict, and the student and counselor document it, Caltech accepts exam scores or a Schoolhouse.world course challenge instead: a 5 on AP Calculus AB, BC, AP Chemistry, AP Physics 1, 2 or C; a 6 or 7 on IB Mathematics HL, Chemistry SL/HL or Physics SL/HL (the catalog says IB Mathematics SL does not qualify); the exams must be taken by the application deadline; the Schoolhouse.world challenge is listed on the admissions site as AP/College Calculus BC, AP/College Chemistry or AP/College Physics 1, while the catalog words it slightly differently (Calculus AB or BC; “High School Physics or AP/College Physics 1”), with proof due within a week of the deadline. The academic-requirements page says these are the only substitutes for “fall 2026” applicants, with no exceptions; check whether the same holds for fall 2027.
• First time in senior year is fine: the site says many students take these subjects for the first time in senior year, but semester or in-progress grades must be reviewable by the application deadline.
• Biology in the Institute core: the catalog says every student takes one biology course (any Bi 1 course, or Bi 8 and Bi 9 with 9 units for grades), plus Ma 1 abc, Ph 1 abc, Ch 1 ab, the first-year chemistry laboratory, programming (CS 1) and others; an Integrated Core pathway (including IC/Bi 1 abc) is an alternative. The catalog’s first-year admission section says biology majors who have passed Bi 8 and Bi 9 (9 units for grades) are considered to have met the Bi 1 requirement. Core courses in the first two terms are graded pass/fail.
• Placement and exemption: the admissions site says all new students take the Foundations Assessment (high-school chemistry, physics and math) and a writing placement exam in the summer; math, physics, chemistry and computer science core courses (Ma 1, Ph 1, Ch 1 ab, CS 1) can be placed out of through summer exams. The pages read do not describe an exemption exam for biology; not published there.
• AP/IB and college credit: the catalog says college credit for AP or IB classes is not automatic; course credit or placement is sometimes granted as the department faculty deem appropriate, at registration each fall. The pages read have no course-by-course table for AP Biology or IB Biology; not published there, so ask the Division of Biology and Biological Engineering.
• Honors track: no honors-sequence entry for biology appears on the pages read; not published there.
• Competitions: the application pages read do not say how biology olympiads or similar competitions are viewed; not published there. The admissions site has a “demonstrating STEM preparedness” page that was not read for this article.

5. Dates and materials (fall 2027)

• Two rounds: Restrictive Early Action (REA, non-binding) closes November 1, 2026, with all required and supplemental materials by November 6, testing done before November 30, decisions (admit, defer, deny) in mid-December and a reply by May 1, 2027. Regular Decision (RD) closes January 4, 2027, with materials by January 10, testing before December 31, 2026, decisions in mid-March and a reply by May 1. One paragraph of the RD text prints the reply date as “May 1, 2026” while the rest of the page says May 1, 2027; go by the latter. REA applicants may not apply early action or early decision elsewhere, with listed exceptions (institutions outside the United States, public universities with non-binding policies, and so on).
• Materials: the Common App or QuestBridge application, the application fee, two teacher letters (one STEM: calculus or beyond, chemistry, physics or biology; one humanities or social science: English, history, government or economics), the School Report from your counselor (who may also write a letter), official transcripts for grades 9 to 11, the Mid-Year Report, and SAT or ACT scores; all AP and IB exams must be reported whatever the score. The catalog adds that supplemental essays are updated on the admissions site each August 1. Optional supplements include a research paper or a STEM or non-STEM portfolio.
• Application fee: the admissions site says USD 85, non-refundable, with waivers for hardship and no fee for QuestBridge applicants. The catalog’s undergraduate expenses page says USD 75; the two differ, so go by the admissions site and check.
• Testing: Caltech requires the SAT or ACT (for fall 2027 applicants the ACT writing and science subscores are not required) and looks at each subscore rather than the ACT composite. The site uses “buckets”: SAT Math or Reading and Writing 780–800 (ACT subscore 35–36) is Bucket A, 750–770 (ACT 33–34) is Bucket B, and the committee sees only the bucket, not the exact score; below 750 (ACT below 33) is Bucket C and the exact score is shown. There is no minimum and no preferred test; superscoring applies. The page adds that successful applicants have traditionally had 700 or higher on each SAT section or 30 or higher on each ACT section, but a perfect score is not expected. Applicants who could not sit for a test can explain in the Caltech-specific application.

6. Domestic students

• Costs (catalog, 2026-27, undergraduate, on campus): tuition USD 68,574, fees USD 2,655, housing USD 12,711, food USD 9,285, total direct costs USD 93,225 as printed; indirect costs (books and equipment USD 1,428, personal USD 3,969) total USD 5,397. Fees exclude the Student Health Insurance Plan (USD 5,388, optional if you have comparable cover); new students also pay a one-time USD 600 orientation fee and a USD 100 general deposit. The catalog says the degree is billed on four years (12 terms). The pages read do not give in-state and out-of-state tuition or any priority or guaranteed admission for residents of a particular state; not published there.
• Aid: the admissions site says Caltech is need-blind for domestic students (including undocumented and DACA students who graduate from a US high school) and meets 100% of demonstrated need; it awards no merit scholarships, only need-based aid, and encourages outside scholarships. Most students from families earning under USD 200,000 (typical assets) can expect a package that covers tuition, and most under USD 100,000 can expect a no-loan package covering tuition, fees, housing and food. For the fall 2026 class the average grant was just under USD 69,000.
• Department scholarships: the pages read do not describe a scholarship specific to the biology department; not published there. Caltech awards no merit scholarships; research support such as the Summer Undergraduate Research Fellowship is mentioned on the admissions site’s undergraduate-research page, so check the website.

7. International students

• Who counts: Caltech defines an international applicant as a non-US citizen or permanent resident attending secondary school outside the United States; asylees, refugees and undocumented students in the US are domestic. Apart from financial-need consideration, application and review are the same for everyone.
• English: required of all international applicants unless English is your native language or the main language of instruction at your secondary school (in that case the site strongly recommends a score). Accepted: Duolingo English Test, IELTS, TOEFL, taken before the deadline. Minimums listed: IELTS 7 overall and 7 in each area; TOEFL (taken before January 21, 2026) 100 and 25 per area; TOEFL (on or after January 21, 2026, 1 to 6 scale) 5 and 5; Duolingo 130 and 130. InitialView (a recorded conversation and writing sample) is recommended, not required, and does not replace an English score.
• Records and materials: official transcripts listing course titles, grades and predicted grades, sent by your school; non-English documents need the original plus an English translation, and no conversion to US grades is needed; an application with any untranslated part will not be reviewed. For international curricula the site adds: IB requires Higher Level Maths, GCE A-Level requires A-Level Maths, and students in India must complete both Year X and Year XII board or CBSE examinations. Students who only take STEM in the last two years (A-Level, for example) need two English and two social-studies classes in the first two years. Two teacher letters are needed here too (an applicant with no humanities or social-science course in the last two years may substitute a letter from a teacher in another core subject).
• Aid: Caltech is need-aware for international applicants because aid funds for them are limited, so need may affect admission, while it commits to meeting the demonstrated need of everyone admitted. An international student who may ever need aid must apply for it when applying for admission; if you do not apply for or receive aid in the first year you cannot apply later (Canadian and Mexican citizens may be an exception); if you receive aid in year one you may reapply each year. The International Financial Aid Statement of Intent is part of the application.
• Proof of funds and credential-evaluation bodies: not stated on the pages read; not published there, so ask Admissions.

8. Applicants from China

• Gaokao: the pages read do not say whether or how Gaokao results are used; not published there, so ask Admissions.
• Transcripts: under the general international rules, your school sends official transcripts (grades 9 to 11, or the equivalent of an international curriculum), with an original and English translation if not in English; the School Report is completed by a counselor. No China-specific rule on school-leaving examinations or credential evaluators appears; not published there.
• Preparation and English: if your school does not offer calculus, physics or chemistry, see section 4 for the alternatives; English requirements are in section 7.
• China-specific pages: the pages read have none; not published there.

9. Transfer students

• Which year the pages describe: the transfer pages say the application and requirements for fall 2027 will be available in late fall and list the requirements for fall 2026 applicants, but their date table prints 2027 dates; check the latest.
• Eligibility: the catalog says applicants must have completed secondary school and then enrolled at a college or university and earned credit; Caltech admits transfer students for the fall term only (not winter or spring), does not admit them to the senior year, and students who already hold a bachelor’s degree are not eligible. Transfers enter as sophomores or juniors and may choose any undergraduate option. The pages read give no special conditions for moving into the biology option; not published there, so ask the Division of Biology and Biological Engineering.
• Dates: applications close February 1, 2027; entrance exams are due February 15; decisions come by mid-April (the catalog says early May, so the two pages differ); the reply deadline is June 1. Transfer admission is non-binding and non-restrictive.
• Materials: the transfer application, a USD 85 fee, math and physics entrance examinations, two college faculty letters (math, science or engineering professors), official transcripts from all colleges and your secondary school, and descriptions of all college-level math and science courses. The catalog says transfer applicants do not submit the SAT and Caltech does not review SAT or ACT scores for them.
• Preparation and the entrance exams: the site says transfer students are presumed to have mastered the first-year core: calculus of one and several variables, linear algebra, classical mechanics, electromagnetism and statistical physics, and special relativity. Caltech looks for these on the transcript and measures preparation with the math and physics entrance exams. After you apply and the February 1 deadline passes, you submit a self-proctor form in the applicant portal and receive the exams electronically; each has a 4-hour limit (8 hours in total, not necessarily on one day), taken on your honor with no references, calculators or electronic devices, and due February 15. The site provides sample questions and a list of the textbooks used in first- and second-year math and physics (PDFs).
• Credit: after admission Admissions gives a preliminary estimate of class standing; after enrolling, the registrar and faculty review your transcripts and syllabi, and Caltech cannot say before admission whether coursework elsewhere will be accepted. Transfer students must spend at least two years (six terms) in residence and earn at least 216 units at Caltech, not counting math and science core courses, and must complete all core courses.
• International transfer students: English requirements are as in section 7 (the transfer page lists TOEFL as total 100 and 25 in each area). No financial aid is available to international transfer and 3/2 applicants, who should expect to cover the full cost. Translations must be done by an official translator, not by the applicant.
• The 3/2 Dual Degree Plan: the catalog says Caltech invites students from 13 selected liberal arts colleges to transfer after their junior year; after two years in residence and completing Caltech’s requirements they receive a Caltech BS and a second bachelor’s degree from their home college, and may enter any option. Applications are due April 1; applicants need at least one year of calculus-based physics and mathematics (two recommended, including multivariable calculus and differential equations) and one year of chemistry.

Checklist

Domestic students:

• Four years of math including calculus, a year of physics and a year of chemistry in high school; apply by November 1, 2026 (REA) or January 4, 2027 (RD)
• Take the SAT or ACT (before November 30 or December 31) and ask two teachers for letters, one STEM and one humanities or social science
• Take the common first-year core and declare the biology option at the end of the first year

International students (including those from China):

• Same dates and materials; submit English scores as required; apply for aid at the same time as admission if you will ever need it
• Ask Admissions how Gaokao results are used and what proof of funds is needed; ask the division how AP and IB credit is handled

Transfer students:

• Have earned college credit; check the latest fall 2027 requirements; apply by February 1, 2027 and return the math and physics entrance exams by February 15

Sources: Caltech, Majors and minors; The first year; Academic requirements; First-year application requirements; Deadlines; Standardized tests; International applicants; Application fee; Undergraduate research; Afford; Transfer deadlines; Transfer requirements; Transfer entrance exams; International transfer applicants; Catalog: biology; Catalog: core requirements; Catalog: first-year admission; Catalog: transfer admission; Catalog: undergraduate expenses. Dates are for fall 2027 entry and costs for 2026-27; the first-year academic requirements page and the transfer pages describe fall 2026 requirements, so check whether anything changes for fall 2027. Check Caltech’s website for the latest.