NBME 27 Score CalculatorThe Bugs & Drugs Step 1 Diagnostic — Reveal Your Microbiology & Pharmacology Gap
200 questions · Week 4–5 mid-dedicated checkpoint. Enter wrong answers or percent correct to get your predicted 3-digit score instantly. NBME 27 is widely regarded as the most Microbiology and Pharmacology-heavy active Step 1 form — a low score signals specific content gaps, not a readiness crisis.
NBME 27 Slightly Overpredicts — Subtract 2–4 Points for Scheduling
NBME 27's Microbiology and Pharmacology weighting means students who prepared those areas heavily score higher than their overall readiness justifies. Community data places average overprediction at 2–4 points. Subtract 2–4 pts from your predicted score before making scheduling decisions. The Step 1 passing threshold is 196.
Why NBME 27 Scores Skew Toward Microbiology and Pharmacology
NBME 27's questions are predominantly single-step recall — stems are shorter and less ambiguous than NBME 28 or NBME 30. A wrong answer almost always traces back to a specific Microbiology or Pharmacology knowledge gap, not to test-taking strategy or clinical reasoning failure. This makes NBME 27 one of the most diagnostically honest forms in the dedicated sequence.
If your Microbiology and Pharmacology preparation is thorough, NBME 27 will score higher than your true readiness — mild overprediction is the result. If you carry gaps in these areas, the score will expose them directly. Either way, NBME 27 is most useful as the Bugs & Drugs diagnostic taken after completing a dedicated Micro/Pharm review cycle.
Your NBME 27 score − 2 to 4 pts = conservative scheduling estimate
Each wrong answer costs 1.11 pts on NBME 27. For comparison, NBME 28 costs only 1.048 pts per wrong answer — the most forgiving slope among active forms. The same 40 wrong answers produce an approximately 1.5–2 point higher score on NBME 28.
What NBME 27 Tests More — and Less — Than Other Forms
Understanding NBME 27's content profile helps you interpret your score correctly and prioritize the right review material before sitting the form.
Microbiology & Pharmacology
Organism ID and gram stain patterns, virulence mechanisms, HIV/AIDS-related conditions, TB, Haemophilus. Autonomic pharmacology (cholinergic/adrenergic agonists & antagonists), antimicrobial adverse effects (Red Man Syndrome, tendon rupture from fluoroquinolones).
Long vignettes & multi-step clinical reasoning
Shorter, more direct stems than NBME 28 or NBME 30. Less ambiguity and fewer distractor-heavy questions. Multi-step deductive reasoning is required less often — knowing the fact is usually sufficient.
Content distribution reflects community observations, not official NBME documentation. Individual question sets vary.
NBME 27 Score Benchmarks — What Your Wrong-Answer Count Means
Subtract 2–4 pts from the predicted score for a conservative scheduling estimate.
| Wrong Answers | Predicted Score | Readiness Signal |
|---|---|---|
| 20 | ~254 | Exceptional — schedule with confidence |
| 30 | ~243 | Strong |
| 40 | ~232 | Above average |
| 50 | ~221 | Solid — verify with NBME 29 |
| 62 | ~208 | Near passing after adjustment — targeted Micro/Pharm review |
| 72 | ~197 | Right at passing threshold |
| 75+ | <196 | Below passing — do not schedule |
NBME 27 score formula: 276.48 − 1.11 × wrong answers. Passing threshold: 196.
NBME 26 / 27 / 28 / 29 — Difficulty & Timing Comparison
| NBME 26 | NBME 27 | NBME 28 | NBME 29 | |
|---|---|---|---|---|
| Slope (pts/wrong) | 1.152 | 1.11 | 1.048 | 1.09 |
| Difficulty | Moderate | Moderate | Easy | Moderate |
| Recommended timing | Week 3–4 | Week 4–5 | Week 5–6 | Week 6–7 |
| Score bias | Slight overpredict | Slight overpredict (+2–4) | Overpredicts +3–5 | Underpredicts ~2 |
| Primary use | Clinical reasoning check | Bugs & Drugs diagnostic | Confidence builder | Readiness check |
Community consensus data. Slope values from regression formulas calibrated against reported score pairs on r/step1 and SDN.
NBME 27 Score Conversion Table — Step 1
| Wrong | Correct | % Correct | Predicted Score | Pass Prob |
|---|---|---|---|---|
| 0 | 200 | 100% | 276 | 99.9% |
| 5 | 195 | 97.5% | 271 | 99.9% |
| 10 | 190 | 95% | 265 | 99.9% |
| 15 | 185 | 92.5% | 260 | 99.9% |
| 20 | 180 | 90% | 254 | 99.9% |
| 25 | 175 | 87.5% | 249 | 99.9% |
| 30 | 170 | 85% | 243 | 99.9% |
| 35 | 165 | 82.5% | 238 | 99.9% |
| 40 | 160 | 80% | 232 | 99.8% |
| 45 | 155 | 77.5% | 227 | 99.6% |
| 50 | 150 | 75% | 221 | 98.9% |
| 55 | 145 | 72.5% | 215 | 96.8% |
| 60 | 140 | 70% | 210 | 92.6% |
| 65 | 135 | 67.5% | 204 | 80.8% |
| 70 | 130 | 65% | 199 | 63.2% |
| 75 | 125 | 62.5% | 193 | 36.8% |
| 80 | 120 | 60% | 188 | 19.2% |
| 85 | 115 | 57.5% | 182 | 7.4% |
| 90 | 110 | 55% | 177 | 3.2% |
| 95 | 105 | 52.5% | 171 | 1.1% |
| 100 | 100 | 50% | 165 | 0.4% |
| 105 | 95 | 47.5% | 160 | 0.2% |
| 110 | 90 | 45% | 154 | 0.1% |
| 115 | 85 | 42.5% | 149 | 0.1% |
| 120 | 80 | 40% | 143 | 0.1% |
| 125 | 75 | 37.5% | 140 | 0.1% |
| 130 | 70 | 35% | 140 | 0.1% |
| 135 | 65 | 32.5% | 140 | 0.1% |
| 140 | 60 | 30% | 140 | 0.1% |
| 145 | 55 | 27.5% | 140 | 0.1% |
| 150 | 50 | 25% | 140 | 0.1% |
| 155 | 45 | 22.5% | 140 | 0.1% |
| 160 | 40 | 20% | 140 | 0.1% |
| 165 | 35 | 17.5% | 140 | 0.1% |
| 170 | 30 | 15% | 140 | 0.1% |
| 175 | 25 | 12.5% | 140 | 0.1% |
| 180 | 20 | 10% | 140 | 0.1% |
| 185 | 15 | 7.5% | 140 | 0.1% |
| 190 | 10 | 5% | 140 | 0.1% |
| 195 | 5 | 2.5% | 140 | 0.1% |
| 200 | 0 | 0% | 140 | 0.1% |
About NBME 27
Interchangeable with NBME 26 for mid-dedicated assessment.
Heavy emphasis on Microbiology ("Bugs & Drugs"). Similar difficulty to NBME 26.
Other Step 1 Practice Exams
NBME 27 Step 1 Calculator — FAQ
This tool is for educational purposes only. Not affiliated with NBME® or USMLE®. Predictions carry an estimated error of ±5–8 points. No peer-reviewed study has published form-specific bias or R² data for NBME 27; accuracy figures and content emphasis observations reflect community consensus from r/step1 and SDN forums.