reviewWe went over questions for CK exam and he pointed out what I was doing when approaching a question. He helped me through different steps to get better in answering questions.
Erika
"Free 120" is what students call the official Step 2 CK sample questions that USMLE publishes. USMLE itself describes them as more than 100 sample Step 2 CK test questions, available as a PDF and as an interactive testing experience (USMLE, Step 2 CK sample test questions). They are the closest thing to the real exam you can practise with for free, so they are worth using deliberately.
Official practice exams
| Topic | Official rule | Source |
|---|---|---|
| Official practice exams | NBME Comprehensive Clinical Science Self-Assessment (CCSSA): seven forms, from $62, four sections of 50 questions; reports an estimated probability of passing Step 2 CK. | NBME: CCSSA |
| Free 120 (sample questions) | More than 100 sample Step 2 CK questions, free, as a PDF and an interactive testing experience; a new interactive version for exams on or after May 7, 2026 uses 30-minute blocks. | USMLE: Step 2 CK sample test questions |
| Passing score | 218 on the three-digit scale, for exams on or after July 1, 2025. | USMLE: results and scoring |
| Results | Typically within four weeks of the test date; USMLE advises allowing at least eight weeks to be notified. | USMLE: results and scoring |
1. Know what the Free 120 is, and is not
- Official: written and released by USMLE, so the style matches the real exam.
- Free: no purchase or registration needed.
- Answer key only: the published questions show the correct answer letter, not written explanations. Any "Free 120 explanations" you find online are written by third parties, not USMLE.
- Not scored: it gives no three-digit score or percentile. For a score estimate, NBME sells separate self-assessments.
Because the items are USMLE's material, we do not reproduce or explain individual questions here. What follows is how to get the most out of them.
2. Use the version that matches your test date
From May 7, 2026, Step 2 CK moved to sixteen 30-minute blocks in a 9-hour day. USMLE says that if your exam is before May 7 you should keep using the current interactive experience, and otherwise review the new one to get used to the 30-minute blocks and updated functions (USMLE). The interactive versions are linked from USMLE's Step 2 CK materials page.
Separately, USMLE offers a paid practice session at a Prometric test centre so you can rehearse the test-centre experience itself. That is about the environment, not extra questions. For the full exam-day timing, see how long Step 2 CK is.
3. Take it at the right point in your study
This part is our advice. Most students get the most from the Free 120 in the last one to two weeks before the exam, once content review is largely done. Taken too early, it mostly shows content gaps you already know about. Taken late, it checks pacing in the real interface and builds confidence on official-style questions.
If you have a dedicated period of several weeks, a common pattern is: NBME self-assessments spread across the period for score tracking, and the Free 120 near the end as a final rehearsal.
4. Sit it like the real exam
- Use the interactive version, not the PDF, so you practise the real interface.
- Do the blocks back to back with timed breaks, in one sitting.
- Same time of day as your real appointment if you can.
- No notes, no pausing to look things up.
5. Review every question, not just the misses
Without written explanations, review takes more work, and that is where the value is. For each question, write one line on why the right answer is right and why your choice was wrong. Do the same for questions you got right by guessing. Then sort every miss into a content gap or a reasoning error, such as misreading the question stem or missing a time cue.
| Miss type | What it looks like | What to do next |
|---|---|---|
| Content gap | You did not know the fact or management step | Targeted review of that topic, then questions on it |
| Reasoning error | You knew it but misread or rushed | Slow down on that question type; practise timed blocks |
| Lucky guess | Right answer, wrong reason | Treat it as a miss |
6. Do not read too much into the percent correct
USMLE does not publish an official conversion from Free 120 percent correct to a Step 2 CK score, so any converter you see is unofficial. For a score estimate with a published method, use NBME's Comprehensive Clinical Science Self-Assessment, which reports an estimated probability of passing. See how accurate NBME practice exams are.
Free 120 percent correct and the 218 passing score
Students often ask what Free 120 score is “safe”. USMLE does not answer that, but it does publish two numbers worth knowing. The real exam’s passing score is 218 on the three-digit scale (USMLE scoring), and on the real exam examinees typically need about 60% of questions right to pass, with the exact share varying from form to form (USMLE Bulletin).
Do not turn that into a Free 120 target. The sample set is a single fixed form that many students have discussed online, so a percentage on it is not equated the way a real score is. Read it alongside a recent NBME form: if both look comfortable, your pacing and reasoning are probably ready; if they disagree, trust the scored NBME estimate and use the Free 120 review to find out why.
7. Fold the results into your last week
Use the misses to choose the final topics to review, not to start new resources. If the Free 120 shows pacing trouble, spend the last days on full timed blocks. If you want help building that last stretch, see Step 2 CK tutoring.
How the Free 120 fits with other practice tests
| Resource | Made by | Cost | Score estimate | Explanations |
|---|---|---|---|---|
| Step 2 CK sample questions (Free 120) | USMLE | Free | None | Answer letters only |
| CCSSA forms | NBME | From $62 per form | Probability of passing | Yes |
| QBank self-assessments, e.g. UWorld | The QBank company | Varies | The company's own estimate | Yes |
A review template you can copy
- Question number and system.
- My answer, the right answer.
- Why the right answer is right, in one line.
- Why mine was wrong, in one line.
- Type: content gap, reasoning error or lucky guess.
- Action: card, note or topic to revisit before test day.
Filling this in for every question takes two or three hours for the full set. That time is the point: it turns a free practice test into a final, personalised review list.
Worked example: using your result
Say you finish with 80% correct. That number alone tells you little, because no official conversion exists. What it does tell you is where the 20% came from. If most misses are reasoning errors in the last third of each block, the fix is pacing practice, not more content. If they cluster in one system, that system gets the final review days.
A last-two-weeks timeline
| Day | What to do |
|---|---|
| 14 | Final NBME form, reviewed the same day |
| 10-12 | Targeted review from NBME misses |
| 7-9 | Free 120 in one sitting, in the interactive version |
| 5-6 | Review the Free 120 with the template above |
| 1-4 | Light review, sleep, logistics; no new resources |
This is our usual sequence; shift it if your exam falls right after a rotation.
Common mistakes with the Free 120
| Mistake | Why it hurts | Better approach |
|---|---|---|
| Doing it in the first week of dedicated | It only confirms gaps you already know | Save it for the last two weeks |
| Using the PDF instead of the interactive version | Misses the real interface and block timing | Use the interactive version |
| Splitting it over several days | No stamina or pacing data | One sitting with timed breaks |
| Converting the percentage to a score | No official conversion exists | Use NBME forms for score estimates |
| Skipping review because there are no explanations | Loses most of the value | Use the review template above |
If you are retaking Step 2 CK
If you have seen the Free 120 before an earlier attempt, a second pass mostly tests memory. Use it for the interface and timing only, and rely on unseen NBME forms for readiness. See failed Step 2 CK for a full retake plan.
Using it during clerkships
Some students use a few blocks of the PDF during core rotations to get a feel for the style before dedicated. If you do, keep the interactive version unseen for the final rehearsal, so the last-week run still shows true pacing.
What the sample questions test
USMLE organises its sample questions by competency, with examples labelled patient care diagnosis, laboratory and diagnostic studies, clinical interventions, and patient safety, among others (USMLE). That matches how the real exam is built: most questions ask what to do next for a patient, not to recall an isolated fact. When you review, note which competency each miss falls under; a cluster in "next step in management" calls for different practice than a cluster in diagnosis.
| Competency (as USMLE labels examples) | What the question usually asks | How to practise it |
|---|---|---|
| Patient care: diagnosis | Most likely diagnosis from a vignette | Timed mixed blocks; review the key finding you missed |
| Laboratory and diagnostic studies | Which test, or what a result means | Tables of tests by condition from your misses |
| Clinical interventions | Most appropriate next step or treatment | Management algorithms; questions in that system |
| Patient safety and communication | Systems and team questions | Short daily sets; read the stem slowly |
Pairing the Free 120 with NBME forms
A sensible pairing is to take your last NBME form about two weeks out for a score estimate, then the Free 120 about a week out for pacing and style. If the NBME result is on target and the Free 120 review shows mostly reasoning errors rather than gaps, you are usually ready. If both show the same content gaps, the last week should go there.
Reviewing the Free 120 with a tutor
The questions with no explanation are the ones where a second reader helps most. In a session we go through your marked misses and lucky guesses, ask you to say out loud which clue you used, and check whether you committed to an answer before looking at the options. Sessions are led by Dr. Sean Moazezi, who sat every USMLE and COMLEX exam he teaches, with Dr. Chelsi Flippo, a pediatric endocrinologist who tutors Step 2 CK. Bring your review sheet and your last NBME score report.