OmegaLearnHow to Prepare for the U.S. National Chemistry Olympiad (USNCO)
HighWhat is the USNCO?
The U.S. National Chemistry Olympiad (USNCO) is a multi-stage competition run by the American Chemical Society (ACS) that selects the four students who represent the United States at the International Chemistry Olympiad (IChO). Roughly 10,000 students take a local section exam each spring; the top nominees advance to a rigorous three-part national exam of multiple choice, free response, and a hands-on laboratory practical. The very best move on to a two-week study camp and, finally, the IChO team.
Format
The national exam has three parts: Part I is 60 multiple-choice questions in 1 hour 30 minutes, Part II is 8 free-response problems in 1 hour 45 minutes, and Part III is a 2-problem laboratory practical in 1 hour 30 minutes.
Who can enter
Any U.S. high schooler can take the local exam. To advance to nationals a student must be a U.S. citizen or permanent resident, under age 20, enrolled in a U.S. school, and not graduating before May of that year.
When & how
Local exams run late February through mid-March through local ACS sections, and the national exam follows in April (April 10โ19 in 2026), usually hosted at universities. Each section nominates a limited number of top scorers, with at most two per school.
How to advance
The top ~1,000 students reach the national exam. Around 20 of the highest scorers are invited to a two-week study camp at the University of Maryland in June, and four are chosen for the U.S. IChO team.
Locals vs. Nationals
The local and national exams are calibrated very differently. The biggest strategic error is preparing for both as one exam โ the jump in organic chemistry depth between them is where most qualifiers get stuck.
Locals โ general chemistry heavy
The local exam leans hard on general chemistry: stoichiometry, gas laws, equilibrium, acidโbase, thermochemistry, kinetics, and electrochemistry. Organic content is basic โ nomenclature, functional groups, and simple reactions. Solid AP-plus general chemistry is usually enough to nominate.
Nationals โ organic goes deep
At nationals the organic chemistry goes significantly deeper: reaction mechanisms, stereochemistry, spectroscopy, and multi-step synthesis. This is the decisive gap. Bridge it with Organic Chemistry by David Klein (see Fundamental) to build real mechanistic reasoning before the national exam.
Official Information
ACS U.S. National Chemistry Olympiad
The official American Chemical Society home page for the USNCO program, with the exam calendar and how to get involved through your local section.
View โUSNCO Rules & Eligibility
Official eligibility requirements, citizenship and age rules, section nomination limits, and the calculator policy for the local and national exams.
View โPrepare for Olympiad Exams
The ACS preparation hub, with the full archive of past local and national exams and detailed solutions for the free-response and lab sections.
View โAbout the International Chemistry Olympiad
The ACS overview of the IChO and how the U.S. team is selected from the study camp each year.
View โU.S. National Chemistry Olympiad overview
A Wikipedia overview of the USNCO, its multi-stage structure, and past results.
View โPractice Tests
Past USNCO exams are the best practice available. Take the local and national papers under real conditions, timing each part separately and writing full solutions, then grade yourself strictly against the official answers.
Official past USNCO exams & solutions (ACS)
The ACS archive of past local and national exams with annotated solutions for the free-response and lab sections, the single best practice source.
View โUSNCO Exams Reference Page
The reference data sheet supplied with each national exam. Practice with the exact constants and periodic table you will have on test day.
View โMock exams & past papers (CODsite)
Student-written mock local, national, camp, and IChO exams with solutions, a great way to keep practicing once you run out of official papers.
View โInternational Chemistry Olympiad problems
The official IChO site with past theoretical and practical problems, the next level of difficulty after the USNCO national exam.
View โPaid Courses & Classes
Art of Problem Solving ChemWOOT
AoPS's olympiad chemistry program, designed by USNCO Study Camp mentors to build the problem-solving skills the national exam rewards.
View โDr. Chen's Academy USNCO Program
A year-round USNCO preparation program with live small-group classes, recordings, and mock exams, run by a longtime IChO and Study Camp coach.
View โJPH Chemistry Olympiad
Online and in-person chemistry olympiad classes from Professor Jianping Huang, targeting state, national, and international exam performance.
View โAralia Education: USNCO Prep
Small-group USNCO preparation classes guiding students through advanced concepts and past-exam practice with expert instructors.
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