NBME 13 to Step 2 CK
Vendor-equated, so it enters the projection exactly as printed.
NBME 13 carries no correction. NBME equates forms 10 through 16 onto a common score scale, so this one carries no correction: the printed score enters the projection exactly as printed. What changes the projection is how recently you took it, not which of these forms it was.
NBME 13 conversion table
Printed score to projected Step 2 CK range, for a form taken in the last month. The range is about a 68% band: roughly two in three students land inside it, which is why it is a range and not a single number. Take the exam further out and the band widens.
| NBME 13 printed | Projected Step 2 CK | Midpoint | Percentile |
|---|---|---|---|
| 200 | 209 to 231 | 220 | 4th |
| 205 | 212 to 234 | 223 | 5th |
| 210 | 216 to 238 | 227 | 8th |
| 215 | 220 to 242 | 231 | 11th |
| 220 | 224 to 246 | 235 | 16th |
| 225 | 228 to 250 | 239 | 22nd |
| 230 | 232 to 254 | 243 | 30th |
| 235 | 236 to 258 | 247 | 39th |
| 240 | 240 to 262 | 251 | 50th |
| 245 | 244 to 266 | 255 | 60th |
| 250 | 248 to 270 | 259 | 71st |
| 255 | 252 to 274 | 263 | 81st |
| 260 | 256 to 278 | 267 | 89th |
| 265 | 260 to 282 | 271 | 95th |
| 270 | 264 to 286 | 275 | 98th |
Rows shaded amber have a projected floor below the 218 pass line. Percentile is against LCME first-takers. Your printed score is never restated as a lower number: where a correction applies it lives inside the math, not on your report.
What NBME 13 actually predicted, for 222 students
The table above is the model. This one is the record. These are 222 students who posted a NBME 13 score and, later, the real Step 2 CK score that followed. Median NBME 13 was 246; their median real score was 259, a jump of +12 points.
| NBME 13 printed | Students | Median real Step 2 | Middle half landed |
|---|---|---|---|
| below 230 | 35 | 252 | 246 to 259 |
| 230 to 239 | 42 | 254 | 249 to 259 |
| 240 to 249 | 54 | 257 | 252 to 261 |
| 250 to 259 | 44 | 263 | 258 to 268 |
| 260 and up | 47 | 269 | 264 to 273 |
Self-reported scores posted to public forums, paired per student. People who do well post more often than people who do not, so treat these as an optimistic ceiling rather than a population average. The middle-half column is the interquartile range: a quarter of students in that band finished below it and a quarter above.
How the projection works
Three steps, and the constants are published rather than described. Then it is shrunk toward the population mean of 250 with a slope of 0.79, which is what stops a single high form from projecting a fantasy. Then 9 points are added for the measured gain from practice form to real exam.
Fit on 258 real posted score reports and tested blind on 32 it had never seen: average miss 4.1 points, bias statistically zero. Reddit posters skew toward good news, so treat the range as honest rather than generous. Full methodology, including where the model stops being trustworthy.
Questions
- Does NBME 13 convert directly to a Step 2 CK score?
- Not one to one. A practice form and the real exam are different tests taken on different days, so the honest output is a range, not a single number. The projection shrinks your form toward the population mean and adds the measured practice to real gain, then reports a band around it.
- Is NBME 13 accurate?
- It is vendor-equated onto the same scale as the other modern forms, so it needs no correction here. Accuracy in the sense that matters, how close the projection lands to a real score, was tested blind on 32 score reports the model had never seen: average miss 4.1 points.
- How much does the date I took it matter?
- A lot, and more than most converters admit. Forms are weighted by recency with a roughly 21 day half-life, and the width of the projected range depends on how far out your exam is. A form from three months ago tells you much less than one from last week.