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They are experts at STEP 2 and got me through it after I had a difficult time passing shelf exams this year.
Sara Z.
A shelf exam is the NBME Clinical Science Subject Exam a medical school gives at the end of a clerkship, such as medicine, surgery or pediatrics. Each discipline exam has 110 questions in 2 hours 45 minutes (NBME timing chart), and the result usually counts toward your clerkship grade.
This page explains which shelves exist, how they are scored and turned into grades, how DO schools differ, and how to prepare for one during a busy rotation.
Exam format at a glance
| Topic | Official rule | Source |
|---|---|---|
| Length | Medicine, Surgery, Pediatrics, Psychiatry, Obstetrics and Gynecology, Clinical Neurology and Ambulatory Care: 2 hours 45 minutes each. Family Medicine Modular: 2 hours 15 minutes to 2 hours 45 minutes depending on modules. A 15-minute tutorial comes first. | NBME: subject exam timing chart (PDF) |
| Questions | 110 for each clinical science discipline exam; Family Medicine Modular has 90, 100 or 110 depending on modules. | NBME: subject exam timing chart (PDF) |
| Scoring | Equated Percent Correct (EPC), on a 0 to 100% scale, representing the percentage of content mastered. | NBME Subject Exam Program Guide (PDF) |
| Passing score | NBME sets none. Its Grading Guidelines help clerkship directors set passing and honors grades, and are reviewed every two to three years. | NBME Subject Exam Program Guide (PDF) |
| Who takes it | Only medical schools can buy the exams; they are given as end-of-clerkship assessments. | NBME: subject exam questions for educators |
| Fee (paid by the school) | $52 per examinee locally, $54 remote, $106 at Prometric, July 2026 to June 2027. | NBME: subject exam fees |
| Results | Often posted to the school the calendar day after the testing window ends, and up to three business days. Students view results in INSIGHTS through the MyNBME Examinee Portal. | NBME Subject Exam Program Guide (PDF) |
Which shelf exams are there?
NBME publishes a clinical science exam for each core clerkship. Times below are testing time; every web exam adds a 15-minute tutorial (NBME timing chart).
| Shelf | Questions | Testing time |
|---|---|---|
| Medicine | 110 | 2 h 45 min |
| Surgery | 110 | 2 h 45 min |
| Pediatrics | 110 | 2 h 45 min |
| Obstetrics and Gynecology | 110 | 2 h 45 min |
| Psychiatry | 110 | 2 h 45 min |
| Clinical Neurology | 110 | 2 h 45 min |
| Ambulatory Care | 110 | 2 h 45 min |
| Family Medicine (modular) | 90 to 110 | 2 h 15 min to 2 h 45 min |
Your school decides which of these you sit and when. Some questions on any form may be unscored field-test items (NBME Program Guide), so a question that seems to come from nowhere may not count.
How shelf exams are scored and graded
NBME reports an Equated Percent Correct score, a 0 to 100 figure meant to show the share of the content you have mastered (NBME Program Guide). It is equated, so a score means the same thing whichever form you get. NBME does not set a passing score; any cut-off, and any comparison with your classmates, is the school's.
The grade is the school's decision. NBME supplies Grading Guidelines that clerkship directors use to set pass and honors cut-offs (NBME Program Guide), and schools weight the shelf differently against ward evaluations. Read your clerkship handbook for the cut-offs that apply to you, and see our shelf percentile guide for how scores are usually compared.
Results tend to be quick: NBME often posts them to the school the day after the testing window closes, and within three business days at most (NBME Program Guide).
Do shelf exams matter?
They matter twice. First, at most schools the shelf is a large part of the clerkship grade, and clerkship grades are what residency programs read in your school's evaluation letter. Second, the shelves test the same clinical science as Step 2 CK and COMLEX Level 2-CE, so the questions you do for each shelf are also Step 2 preparation. Students who treat each shelf as a block of Step 2 study usually arrive at dedicated time with less to relearn.
DO students: shelf exams or COMAT?
Osteopathic schools choose. Some give the NBME shelves; others use NBOME's COMAT series, nationally standardized subject exams written for osteopathic students (NBOME COMAT). The preparation is similar, but COMAT exams include osteopathic principles, so check with your clerkship coordinator which exam you will sit before you buy practice material.
How to prepare during the rotation
You will not get a dedicated study period for a shelf. The plan has to fit after clinical duties, which is why the sample below runs about two hours a day:
- Questions from week 1. Twenty timed questions a day, reviewed fully, does more than a weekend of reading at the end.
- Read on your own patients. The conditions you see on the wards are the easiest ones to remember on test day.
- Two official checkpoints. NBME's Clinical Science Mastery Series forms are 50 questions for $21 and come with a table that converts the result to the subject exam scale (NBME Mastery Series). Take one mid-rotation and one in the last two weeks.
- Practise the length. Before the exam, sit at least one 110-question timed set in one go.
Sample 8-week Internal Medicine clerkship shelf schedule
Sample schedule
Sample schedule for illustration only. Not a real student, not real data. Your tutor builds your actual plan around your practice-exam results and the time you have.
Sample 8-week Internal Medicine clerkship shelf schedule: 8 weeks, about 2 hours a day, 6 days a week. One day off each week.
A typical day
| Block | Hours | What |
|---|---|---|
| Question bank | 1 | 20 questions after clinical duties, full review |
| Anki review | 0.5 | Due reviews |
| Content review | 0.5 | Read on your own patients’ conditions |
Week by week
| Week | Focus | Practice exam |
|---|---|---|
| Week 1 | Cardiovascular | |
| Week 2 | Respiratory | |
| Week 3 | GI | |
| Week 4 | Renal / Urinary | Medicine |
| Week 5 | Endocrine | |
| Week 6 | Heme / Onc; Immune / ID | |
| Week 7 | Weakest areas from self-assessment | Medicine |
| Week 8 | Mixed timed blocks; Shelf exam (110 questions, 2 hours 45 minutes) |
NBME Clinical Science Mastery Series self-assessment (50 questions, $21) in weeks 4 and 7; its conversion table maps to the shelf score scale.
If a shelf goes badly
NBME sells the exams to schools and leaves retake rules to them, so your clerkship handbook decides whether and when you can resit. What a tutor can do is find the reason. In sessions we work NBME-style questions live, and the pattern is usually visible within an hour: reading the last line too late, changing right answers, or not committing before looking at the options. Sean Moazezi tutors shelf exams alongside Step 2 CK, and the habits that fix a shelf score carry straight into Step 2.