The HMChO is an international chemistry competition founded by students from Harvard and MIT, aiming to challenge and inspire high school students to go beyond chemistry school curriculum by providing a rigorous assessment modeled after the U.S. National Chemistry Olympiad.

Any high school student (equivalents of U.S. grades 9-12) worldwide can register (all students participate in the same division). 

The exam will be held on February 21, 2026.  

No, the 2026 competition will be conducted entirely online. However, we are working on having future competitions transition to an in-person format.

The competition consists of two parts:  

- Part I: 60 multiple-choice questions (90 minutes);  

- Part II: 8 written-response problems (105 minutes, additional 15 minutes for file scanning and upload);  

- Break: 30 minutes between Part I and Part II. 

See the "How should I best prepare for HMChO?" FAQ below to see more detailed syllabus information and preparation advice.

The exam is conducted online via Gradescope, with live proctoring through Zoom.  Students will receive a Zoom link and an invitation to join HMChO 2025 on Gradescope before the competition. For more details about exam security and regulations, see the Information page.

Students must join their assigned Zoom session 15 minutes before the exam. Proctors will conduct an identity verification check in a one-person breakout room before allowing students to enter a larger ten-person breakout room.

Students must position their webcam at an angled side view, ensuring their workspace (table and writing surface) and part of their upper body (hands and head) are visible throughout the exam.  For more examples of proper and improper setups, see the Information page.

Students may not leave their rooms during the 90-minute and 105-minute examination periods. However, they may take a break during the 30-minute intermission between Part I and Part II. 

We are only offering accommodations such as permission for a medical device on the desk (e.g, glucose monitors) and permission for more bathroom breaks due to medical reasons (e.g, kidney problems), so after you complete the registration form, we will reach out to see if we can work this out for you.

There will be a practice test available on Gradescope before the competition, which we strongly recommend students try out in order to familiarize themselves with the platform and submission process. 

The total score is calculated as: Total Score = (1.25 × Part I Score) + Part II Score, where Part I is 60 multiple choice questions worth 60 points in total and Part II is 8 free written-response questions worth 100 points total.

If students receive the same score, tiebreakers are applied in this order:  

1. Higher Part II Score;  

2. More correct answers on difficult Part II problems;  

3. More correct answers on difficult Part I questions. 

Appeals will not be accepted unless there is a clear error in the answer key. In such cases, students must submit an appeal to hmcho.inquiries@gmail.com within 24 hours of the answer key being published. 

Participants will receive certificates as follows:

- Top 10 Students - For the top 10 students;

- High Honors – For the top ~5% of students; 

- Honors – For the next 10% of students (for the top ~15% of students overall).

The 2026 competition is based on the US National Chemistry Olympiad (USNCO) National Part I and Part II exams. 

Content to Study:

Both the Part I and Part II exams will cover the following subjects: stoichiometry, descriptive chemistry/laboratory techniques, states of matter, thermodynamics, kinetics, equilibrium, oxidation-reduction, atomic structure/periodicity, bonding/molecular structure, and organic chemistry. 

• Part I (like USNCO past papers) will have 6 multiple choice questions on each of the 10 above subjects. The subjects are presented in the order above on the exam.

• Part II (like USNCO past papers) will have 8 multi-part questions chosen from the above topics. 

  • Question 1 is advanced stoichiometry and quantitative analysis.

  • Question 5 requires students to predict products from inorganic (4 reactions), organic (1 reaction), and nuclear (1 reaction) reactions.

  • Question 6/7 is typically short-answer written questions asking you to explain inorganic/structural/bonding phenomena.

  • Question 8 is organic chemistry.

  • The remaining questions are typically quantitative problems chosen from the physical chemistry subjects.

Key content knowledge can be established from a University-level general chemistry textbook (Zumdahl, Atkins, etc.), supplemented with organic chemistry (e.g. Klein). AP Chemistry provides a gateway to USNCO and further advanced study in chemistry.

For the reference of international students, U.S. Chemistry Olympiads emphasize challenging physical chemistry (particularly thermodynamics, kinetics, equilibrium, and electrochemistry) more than foreign national Olympiads and IChO. Conversely, inorganic reactions and organic chemistry are heavily de-weighted and less difficult in the US, with only ~12% of the exam consisting of organic chemistry. 

Practice Exams:

The "Past HMCHOs" tab on our website contains our previous exams with detailed solutions, which can provide an opportunity for practice and review.

In addition, reviewing past USNCO National Part I and Part II exams provides additional practice with questions from the same format and syllabus. Note: USNCO also has a Local Exam at the link above, which is significantly easier than USNCO National Exam. Do not get the two exams confused, scroll past the Local Exam papers to find the past National Exam papers.

HMChO tends to be a step above USNCO Nationals in problem solving difficulty, though does not cover syllabus material that is not allowed for USNCO. This allows students from all skill levels (from introductory chemistry, to IChO medalists) to find both approachable and challenging questions that merit future study.

It is not anticipated that top scorers are close to perfect on HMChO or USNCO; what matters more is solving all problems you can in a timely fashion.