What is the USNCO?
The U.S. National Chemistry Olympiad (USNCO) is the American Chemical Society's annual high-school chemistry competition. Its purpose is to identify the four students who represent the United States at the International Chemistry Olympiad (IChO) each summer.
USNCO has been administered by the American Chemical Society since 1984. It runs through ACS Local Sections β geographic chapters of the society spread across the United States β each of which administers its own Local Exam and nominates top students to the National Exam. There is no single centralized testing facility; students take the Local Exam at their school or local proctored site under the supervision of the ACS Local Section that covers their region.
USNCO is distinct from regional and state-level chemistry competitions in two ways: it is the official U.S. selection mechanism for the international team, and its exam content closely tracks the IChO syllabus, covering topics that go well beyond a typical AP Chemistry course (advanced organic, physical chemistry, inorganic, analytical, and hands-on laboratory technique).
Who is eligible?
Eligibility tightens at each stage of the competition.
Local Exam. Open to any high-school student (typically grades 9-12; some Local Sections allow advanced 7th or 8th graders) enrolled at a U.S. high school within the section's geographic boundaries. No prior USNCO participation is required.
National Exam. Restricted to students nominated by their Local Section. Each section nominates a fixed allotment (typically around 12), drawn from the top scorers β with a key constraint: no more than two students per high school may advance, regardless of how many top scorers a single school has. The detailed nomination mechanics β including how the per-school cap affects selection β are walked through on the USNCO Insider page.
Study Camp and IChO team. Reserved for the top 20 students nationally on the National Exam, who must be U.S. citizens or permanent residents to be eligible for international team competition.
The three stages
The USNCO progression takes a single school year. Each stage filters down to the next.
Stage 1 β Local Exam
~Top 1,000 advanceHeld in March each year. Administered by individual ACS Local Sections. Format is typically 60 multiple-choice questions in 1 hour 30 minutes, covering general high-school chemistry. Roughly the top scorers in each section (within the per-school and citizenship constraints) advance to the National Exam.
Stage 2 β National Exam
Top top 190 awardedHeld in mid-to-late April. Three parts: Part I (multiple choice, ~1.5 hrs), Part II (free response covering reaction writing and extended chemistry problems, ~1.75 hrs), and Part III (a hands-on laboratory practical, ~1.75 hrs). Awards: top top 50 earn High Honor; top top 190 earn Honor; additional students receive Honorable Mention.
Stage 3 β Study Camp
Top top 20 nationallyTwo-week intensive program held at the U.S. Air Force Academy in early June. The top 20 students from the National Exam are invited. Includes advanced instruction, laboratory training, and a final selection examination. The four students with the highest combined performance form the U.S. IChO Team for that summer's International Chemistry Olympiad.
Exam format
The National Exam is the centerpiece of the competition and has three structurally distinct parts.
Part I β Multiple Choice
60 questions in 1 hour 30 minutes. Broad topical coverage β general chemistry, stoichiometry, equilibrium, thermodynamics, kinetics, acid-base, electrochemistry, organic, and brief inorganic. Tests speed, breadth, and rapid pattern recognition. Each question carries equal weight in the raw Part I score.
Part II β Free Response
1 hour 45 minutes of extended-response problems. The first question is always a set of reaction-equation prompts where students must complete and balance chemical reactions across organic, inorganic, and biochemical contexts. Subsequent problems cover quantitative chemistry: detailed thermodynamic analysis, kinetics derivations, multi-step mechanism work, and inorganic structural reasoning. Part II discriminates strongly among serious contenders. The dcho.us Reaction Writing Study Guide covers all 163 reaction-writing questions from 1999 through 2025.
Part III β Laboratory Practical
1 hour 45 minutes of hands-on laboratory work. Typical procedures include titration, qualitative analysis, kinetics measurements, and quantitative determination of an unknown. Scored on procedural technique, data analysis, and final answer accuracy. Part III only counts toward Study Camp selection β not Honor or High Honor ranking. The dcho.us USNCO Lab Practical Guide documents Part III procedures and analysis from 2015 through 2025.
Scoring and award tiers
Tier-specific score formulas determine the Honor and High Honor cohorts as well as Study Camp selection. The lab practical (Part III) is weighted only for Study Camp selection.
| Tier | Cohort | Score formula |
|---|---|---|
| Study Camp | Top 20 nationally | Part I Γ 1.25 + Part II + Part III Γ 0.5 |
| High Honor | Top top 50 | Part I Γ 1.25 + Part II |
| Honor | Top top 190 | Part I Γ 1.25 + Part II |
| Honorable Mention | Additional students below Honor | β |
Exact cutoff scores shift year to year based on cohort performance. For full selection mechanics including how Local Section nomination caps affect who reaches the National Exam, see the USNCO Insider page.
2026-2027 calendar
Standard milestones for the current cycle.
National Exam dates are uniform across all ACS Local Sections. Local Exam dates vary slightly by section. For the dcho.us program calendar β including instruction modules and bootcamps that align with these milestones β see /programs.
How to prepare
Preparation strategy depends on the target tier and the student's starting point.
Local Exam qualification
A student with a solid year of high-school chemistry (or AP Chemistry in progress) and 6-12 months of focused review typically has a strong shot at Local Exam advancement. Emphasis: breadth, stoichiometric fluency, and rapid multiple-choice technique.
National Exam awards (Honor or higher)
12-18 months of preparation covering organic chemistry, physical chemistry, and olympiad-style problem solving in depth. Part II reaction-writing proficiency becomes the discriminator. Mock exams with detailed analysis separate Honor from High Honor.
Study Camp / IChO team
Multi-year commitment, typically starting in 9th or 10th grade. Coverage beyond AP-level into advanced organic mechanisms, statistical thermodynamics, inorganic structure, and analytical lab technique. Sustained year-round practice including frequent mock exams.
For students unsure of where to start, the dcho.us Find Your Level wizard gives a personalized recommendation in about two minutes. Available in English and δΈζ.
Free study resources
Three substantial reference resources are published openly on dcho.us β usable by any USNCO student regardless of coaching program.
- USNCO Reaction Writing Study Guide β every Part II reaction-writing question from 1999 through 2025, with worked answers and a first-principles framework. Filterable by year, reaction type, and topic.
- USNCO Lab Practical Guide β Part III procedures, analysis, and scoring breakdowns from 2015 through 2025.
- Recommended USNCO Textbooks β curated list of reference and problem books organized by competition level and topic.
- Decoding of Chemistry Olympiad (YouTube) β Dr. Chen's free video series covering USNCO problems, reaction-writing strategy, lab practical preparation, challenging topics, learning objectives, USNCO introductions, and study strategies.
- USNCO Insider β selection mechanics: nomination funnel, per-school cap, score formulas, and award tiers.
Dr. Chen's Academy programs
Beyond the free reference materials, Dr. Chen's Academy offers structured coaching programs aligned with the three USNCO progression tiers.
Level 2
Local Prep
For students with one year of solid chemistry experience targeting Local Exam qualification.
Level 3
National Prep
For students with AP Chemistry mastery (or equivalent) preparing for the National Exam.
Level 4
Camp Prep
For advanced students targeting High Honor and Study Camp selection.
Full pricing, schedule, and module-level detail are on the programs page. Outcomes β 10+ IChO medalists, 40+ Study Camp qualifications, 200+ National Exam awards across 15+ years β are detailed on /achievements.
Frequently asked questions
What is the USNCO?
The U.S. National Chemistry Olympiad (USNCO) is the American Chemical Society's annual high-school chemistry competition. It selects the four-member U.S. team that represents the United States at the International Chemistry Olympiad (IChO) each summer. USNCO has been administered by ACS since 1984 and runs through the network of ACS Local Sections across the country.
Who is eligible to take the USNCO?
Any high-school student (grades 9-12 typically; some Local Sections allow younger students) enrolled at a U.S. high school may take the Local Exam, the first stage. Advancement to the National Exam is reserved for the top performers in each Local Section, capped at two students per school regardless of how many high-scorers a school has. Eligibility for the Study Camp and the four-member IChO team requires U.S. citizenship or permanent residency. Local Sections vary in how they organize and proctor the Local Exam β check with the ACS Local Section that covers your school.
What are the stages of the USNCO competition?
The USNCO competition runs in three stages each year. Stage 1 β the Local Exam β is held in March; roughly the top 1,000 scorers nationwide advance. Stage 2 β the National Exam β is held in mid-to-late April and consists of three parts: Part I (60 multiple-choice questions, 1 hour 30 minutes), Part II (free-response problems including reaction equations and quantitative chemistry, 1 hour 45 minutes), and Part III (a hands-on laboratory practical, 1 hour 45 minutes). The top top 190 on the National Exam receive awards. Stage 3 β the Study Camp β is held in early June at the U.S. Air Force Academy and brings together the top 20 nationally for two weeks of intensive instruction and competition. The four students with the highest combined performance at Study Camp form the U.S. IChO team.
How is the USNCO scored?
The National Exam uses tier-specific score formulas. The Honor tier (top ~190 students) and High Honor tier (top ~50 students) are ranked on a Part I Γ 1.25 + Part II composite. The Study Camp cohort (top 20) is selected on Part I Γ 1.25 + Part II + Part III Γ 0.5 β the lab practical only counts toward Study Camp selection. Honorable Mention recognizes additional students below the Honor cutoff. The exact cutoff scores vary year to year based on cohort performance.
When are the USNCO exams held?
The 2026-2027 USNCO cycle follows the standard schedule: Local Exam late Feb - mid Mar, 2027, National Exam mid Apr, 2027, and Study Camp early Jun, 2027. The exact date of each exam within its window is set by the ACS USNCO program office and communicated through Local Section coordinators. National Exam dates are uniform across all ACS Local Sections; Local Exam dates vary slightly by section.
How do I qualify for the USNCO Study Camp?
The Study Camp is reserved for the top 20 students nationwide on the National Exam, ranked on the formula Part I Γ 1.25 + Part II + Part III Γ 0.5. Practically, a Study Camp invitation requires strong performance across all three parts β particularly the Part III lab practical, which only counts toward Study Camp selection. Students who reach the Study Camp typically have multi-year preparation: deep mastery of general, organic, physical, inorganic, and analytical chemistry; hands-on lab experience; and exposure to olympiad-style problem solving. See the detailed selection mechanics on the USNCO Insider page.
What study materials should I use to prepare for the USNCO?
Strong preparation combines textbook foundations, problem-solving practice on real past exams, and (for the Part II reaction-writing section) targeted reaction-mechanism work. Recommended textbook starting points by competition level and topic are listed on the Recommended Textbooks page on dcho.us. The Reaction Writing Study Guide on dcho.us covers all 163 reaction-writing questions from USNCO Part II between 1999 and 2025, with worked answers and a first-principles framework. The Lab Practical Guide covers Part III procedures and analysis from 2015 through 2025. All three resources are free to any USNCO student regardless of coaching program.
How long does USNCO preparation typically take?
Preparation timelines depend on starting level and target outcome. A student aiming for Local Exam qualification (entry to the National Exam) typically prepares 6-12 months with a solid AP Chemistry foundation. A student targeting National Exam awards (Honor or higher) typically prepares 12-18 months covering organic chemistry, physical chemistry, and olympiad-style problem solving in depth. A student targeting Study Camp typically commits multi-year preparation starting in 9th or 10th grade, with sustained year-round practice. Dr. Chen's Academy structures this as a three-level progression β Local Prep (Level 2), National Prep (Level 3), and Camp Prep (Level 4).