As you transition from preclinical coursework to your clinical rotations, you’ll hear a lot more about the NBME Subject Examinations, aka shelf exams. These tests in core clerkships like Internal Medicine, Surgery, Pediatrics, OB/GYN, and Psychiatry offer medical schools and residency programs a standardized way to compare performance across students. Because of that, your shelf exam percentiles become an important part of how your clinical knowledge and progress are evaluated.
At the same time, shelf exams can feel…mysterious. You receive a numerical score and a percentile, but it’s not always clear what those numbers actually represent or how they’ll impact your clerkship grade. How competitive is a certain percentile, and how does the NBME determine these national rankings?
To help you make sense of it all, this guide breaks down the most common questions students have as they move through their rotations, including:
- How should you interpret shelf exam percentiles in the broader context of your grades and residency preparation?
- Can you compare scores at different points in the year?
- How do medical schools use this data, and will residency programs ever see it?
Before diving into those answers, let’s start with the basics: what shelf exams actually are, how they’re scored, and what goes into generating the shelf exam percentiles you see on your score report.
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What are shelf exams?
Shelf exams are standardized tests created and administered by the National Board of Medical Examiners (NBME) to assess how well students can apply knowledge they acquired during a rotation. This makes them quite different from your preclinical exams, which more or less tested your ability to memorize what you’d learned in class.
You’ll take shelf exams for internal medicine, surgery, pediatrics, psychiatry, obstetrics and gynecology, family medicine, and occasionally for elective subjects like emergency medicine or neurology.
Each shelf has approximately 110 multiple-choice questions, and is completed in under three hours.
Because shelf exams are taken at the end of each rotation, students have to find time to study while logging long hours at the hospital. It’s important to know this going into your rotations, so you can create a manageable study schedule.
To learn more about shelf exam format and content, be sure to check out the NBME website.
What are shelf exam percentiles?
After you complete a shelf exam, your score is reported as a scaled score and as a percentile. The raw number of questions you answered correctly is adjusted, accounting for the relative difficulty of your specific exam form.
Because the NBME continuously refreshes its question bank, not every group of students takes the exact same version of a shelf exam. If your version of the pediatrics shelf exam happened to be slightly more difficult than average, your score would be adjusted upward to reflect that.
The percentile rank represents how your performance stacks up against a national reference group of U.S. medical students who took the same exam within the same time frame of the academic year. For instance, scoring in the 70th percentile means you performed better than 70% of students in that reference group and below 30%.
To learn more about shelf scoring, check out the NBME guidelines.
How to Interpret Your Shelf Exam Percentiles
Your percentile is best interpreted as a relative performance indicator.
A percentile in the 50s represents solid, national-average performance and is sufficient for most rotations.
Percentiles between the 55th and 75th typically fall into high pass territory and reflect above-average mastery.
Percentiles above the 75th are considered excellent and are usually associated with honors designations if you’re only considering the shelf.
Your shelf exam percentile can depend on when you test!
An important detail is that percentiles aren’t static throughout the year. This matters because the average performance of test-takers tends to improve as the year progresses.
For example, imagine an MS3 going through the core clerkships completing OB/GYN, IM, and Pediatrics and then taking the Family Medicine shelf later in the year. This means they scored better on that exam given all of the knowledge and experience he/she picked up on prior rotations. Compare that to a fresh MS3 starting out on Family Medicine for the first rotation and taking the shelf after just four weeks without other rotations under their belt.
As a result, the same raw or scaled score can correspond to different percentiles depending on when you take the test. For example, a raw score of 76 might correspond to the 65th percentile in Quarter 1, but only the 55th percentile in Quarter 3, simply because the overall pool of test-takers has gained more clinical experience by that point.
So remember that a “lower” percentile late in the year does not necessarily mean you performed worse—it might just reflect a higher-performing national cohort.
How Schools Use Shelf Exam Percentiles
While the NBME provides the raw and percentile data, each medical school determines how these scores factor into final clerkship grades. Depending on the school, the shelf exam typically counts for 30–50% of the final grade, with the remaining portion determined by clinical evaluations, professionalism, and other assessments such as standardized patient exams or written assignments.
Many schools are transitioning to pass/fail grading, but some of them use percentile-based thresholds to distinguish among pass, high Pass, and honors designations. For instance, one medical school might require at least the 5th percentile to pass, the 60th percentile for high pass, and the 80th percentile for honors.
The exact cutoffs vary not only by institution but also by discipline. Surgery shelves often have slightly higher thresholds for honors, while psychiatry or family medicine may have lower ones due to differences in national averages. The important takeaway is that percentiles—not raw scores—drive most grading decisions.
Why Shelf Exam Percentiles Matter
Even though residency programs don’t see your shelf exam scores directly, they still matter because they influence your transcript and dean’s letter (MSPE). Additionally, honors designations (if your school has them) in core clerkships can enhance your application, especially in competitive specialties.
Shelf exams also serve as a stepping stone to Step 2 CK and are a good predictive indicator for Step 2 performance. Because the question style, pacing, and clinical focus closely mirror the USMLE format, consistently high shelf percentiles are one of the best indicators of readiness for Step 2.
Conversely, if you consistently score below the national average, it may be a sign that you need to refine your test-taking strategy or knowledge integration before taking Step 2. Many students who struggle on shelf exams benefit from incorporating dedicated Step 2 Qbanks earlier in their rotations.
Lastly, schools use shelf performance to determine eligibility for honors societies such as Alpha Omega Alpha (AOA) or to nominate students for departmental awards to further boost their competitiveness.
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How do I improve my performance on shelf exams?
Success on shelf exams isn’t about cramming the week before. The most effective approach—and you’ll hear this same advice from everyone—is to integrate studying into your day-to-day clinical experiences. As you encounter real patients, identify related conditions or topics to review that evening.
For example, if you admitted a patient with decompensated heart failure, review diuretic management, cardiomyopathy differentials, and the next diagnostic steps. This contextual learning improves both retention and understanding, not to mention it’ll make you look like a star on wards.
Recall that the timing of shelf exams throughout the academic year helps maintain momentum. As you move from one rotation to another, build on previously learned material—internal medicine concepts, for example, will reappear in surgery, family medicine, and even psychiatry shelves. Viewing the exams as cumulative assessments rather than isolated hurdles encourages long-term retention and prepares you for Step 2 CK.
Final Thoughts
We hope this guide has helped clarify some of the mystery around shelf exam percentiles, from understanding what they actually represent to how they factor into clerkship grades and residency applications. Knowing how to interpret your score report is an important part of navigating your clinical year with confidence.
As you move through each rotation, keep focusing on steady, integrated studying rather than last-minute cramming. The more you connect what you’re seeing in the hospital or clinic with high-yield concepts, the more prepared you’ll feel when exam day arrives. And remember: strong shelf performance isn’t just a box to check—it’s also one of the best predictors of how you’ll perform on Step 2!
For more (free!) content to help you through clinical years, check out these other posts on the blog:
