It's the last week before Step 2 CK. You've finished your question bank (or you're close), you've done a few self-assessments, and everyone keeps telling you to "do the Free 120." But nobody explains what to actually do with it, or what it means if your percent correct comes back lower than you hoped.
If that's where you are, you're in good company. The Free 120 is one of the most talked-about Step 2 CK resources, and one of the most misunderstood.
Here's what it is, when it fits into your schedule, and how to get real value out of it.
What Is the NBME Free 120 for Step 2 CK?
The NBME Free 120 Step 2 CK set is a free collection of official sample questions published by USMLE and NBME on the NBME orientation site (orientation.nbme.org). As the name suggests, it's roughly 120 questions, written by the same organization that writes the real exam and delivered in an interface that closely mirrors what you'll see at Prometric.
Most students take it in the final 3–7 days before their exam, under timed conditions, as a last confidence check and a test-day dress rehearsal. It does not give you an official three-digit score or a percentile. What you get is a percent correct and, more importantly, a set of questions that show you exactly how the test writers think.
The sample is updated periodically to reflect the current exam content, so always use the version on the official site rather than an old PDF someone passed around in your class group chat.
Don't confuse it with the free Step 2 CK Free 120 diagnostic on MedSchoolGuru. That's a separate, free 120-question set with different questions, and unlike the NBME version it gives you a scaled score estimate and a pass-likelihood readout. Because it doesn't use up the official questions, it works well as an earlier checkpoint in dedicated.
Why the Free 120 Matters More Than Its Size Suggests
A set of around 120 questions is tiny compared to the thousands you'll do in a QBank. So why does everyone treat it like a big deal?
It's Written by the Test Makers
Third-party question banks are excellent for volume and teaching, but they're still approximations. The Free 120 comes from the source. The question stems, the length, the way distractors are built, and the level of detail in the vignettes all reflect real NBME style. That makes it a calibration tool more than a content tool.
It Shows You the Real Interface
Test day is not the moment to figure out where the lab values button is or how the highlighter behaves. Taking the Free 120 in its official interface means the buttons, timer, and layout feel familiar when it counts.
It Tests Your Endurance and Pacing
Step 2 CK on or after May 7, 2026 is sixteen 30-minute blocks with no more than 20 questions per block, in one 9-hour session with at least 55 minutes of break time. Taking several Free 120 blocks back to back, at real pace, gives you a taste of that rhythm. If you find yourself rushing the last few questions of every block, that's a pacing problem you can fix before test day.
When and How to Take It
Step 1: Schedule It for the Final Week
Most students take the Free 120 somewhere between 3 and 7 days before their exam. That leaves enough time to review every question carefully without turning it into a last-minute panic. Avoid taking it the night before. You want time to absorb the lessons and rest.
Step 2: Simulate Test Conditions
Sit at a desk, put your phone in another room, time each block, and take short breaks between blocks the way you would at Prometric. The more realistic the setup, the more useful the pacing information.
Step 3: Review Every Question, Not Just the Misses
For each question, ask yourself why the right answer is right and why each wrong answer is wrong. For questions you got right by guessing or narrowing down to two, review those as carefully as your outright misses. Those near-misses are where the last few points usually hide.
Step 4: Turn Patterns Into a Short Final List
Don't try to relearn medicine in the last few days. Instead, look for patterns. Are you missing "next best step in management" questions? Biostatistics? Ethics? Write down a short list of 5–10 high-yield fixes and spend your remaining days on those.
Optional: Take It in a Prometric Practice Session
Prometric offers paid practice sessions that let you sit sample material in an actual test center. It's not necessary for everyone, but if you get anxious in unfamiliar environments, a dry run can take some of the edge off test day.
How Predictive Is Your Free 120 Score?
This is the question everyone actually wants answered. The honest answer: it's a useful signal, but it's not an official score predictor.
There's No Official Conversion
NBME doesn't publish a conversion from Free 120 percent correct to a Step 2 CK three-digit score. Any conversion table you see online is crowdsourced from student reports, which can be helpful for a rough sense of direction but shouldn't be treated as precise.
Use It Alongside Your Self-Assessments
Your best estimate of where you'll land comes from looking at several data points together: your NBME CCSSA forms (7 available, starting at $62, each giving an estimated probability of passing), other full-length self-assessments, and your recent question bank performance. The Free 120 is one more point on that graph, not the whole graph.
What a Strong Result Usually Means
If your Free 120 percent correct is in line with or above what your self-assessments suggested, that's reassuring. It generally means your knowledge is translating to NBME-style questions and your pacing is solid. Go into test day with confidence.
What a Lower Result Usually Means
If it comes back lower than expected, don't panic. Look at why. A rough set of blocks after a bad night's sleep is very different from a consistent gap in one specialty. If your other self-assessments have been steady, one sample set shouldn't override them. If everything is trending down and you're nowhere near your goal, that's a conversation worth having about whether to adjust your test date, keeping in mind that Prometric appointment change fees rise the closer you get (no fee at 46+ days out, $35 at 31–45 days, $100 at 6–30 days, and $178 for Step 2 CK at 5 or fewer days).
What Most Students Get Wrong About the Free 120
The first mistake is taking it too early. Some students burn the NBME Free 120 Step 2 CK set as a baseline weeks before the exam, then have nothing official left to use as a final calibration. If you want an early baseline, a CCSSA form or MedSchoolGuru's free Free 120 diagnostic is a better fit.
The second mistake is treating it as a content review. Around 120 questions can't cover the breadth of Step 2 CK. Its value is in the style, the interface, and the pacing, not in filling every content gap.
The third mistake is skimming the review. The questions you'll learn the most from are the ones you got right for shaky reasons. A rushed review throws away the best part of the resource.
The fourth mistake is letting a single percent correct define your confidence. It's one data point at the very end of a long process. Read it in the context of everything else you've done.
Building Up to the Free 120 the Right Way
The Free 120 works best as the final check on a foundation you've already built with thousands of exam-style questions and regular self-assessments. The Step 2 CK Question Bank from MedSchoolBro gives you 2,000+ NBME-style questions plus 7 self-assessment forms, so you walk into your final week already used to the style and with plenty of data on where you stand. Then the Free 120 confirms what you already know instead of surprising you.
If you're mapping out the weeks before that final check, our guide on how to score 250 on Step 2 CK walks through the bigger plan.
Frequently Asked Questions
Is the NBME Free 120 Step 2 CK set actually free? Yes. The sample questions are published at no cost by USMLE and NBME on the official orientation site. Prometric also offers paid practice sessions if you want to take sample material in a real test center, but that's optional.
When should I take the Free 120 for Step 2 CK? Most students take it 3–7 days before their exam. That gives you time for a thorough review and a short list of final fixes without cramming the night before.
Does the Free 120 give you a three-digit score? No. You get a percent correct, not an official score or percentile. There's no NBME-published conversion, so use your CCSSA forms and other self-assessments for a better score estimate.
Is there another free 120-question practice test for Step 2 CK? Yes. MedSchoolGuru offers its own free Step 2 CK Free 120 diagnostic on MedSchoolGuru, separate from the official NBME set. It's timed and gives you a scaled score estimate and pass likelihood, so it's a good earlier checkpoint while you save the NBME Free 120 for your final week.
Should I retake the Free 120 if I've already done it? Retaking it can still help with pacing and interface familiarity, but your percent correct will be inflated because you remember the questions. Use it for review and rhythm, not for prediction.
