Model comparison
Mercury 2 vs o3-pro
o3-pro is the stronger model overall, scoring 42.9 to 39.1 on the Noometry Index. Mercury 2 costs 93× less per token, which makes it the better buy when o3-pro's lead doesn't matter for your workload.
Last verified . 2 shared benchmarks.
Summary
- They share 2 benchmarks with published results for both. Mercury 2 scores higher in 2 categories and o3-pro in 3 categories; 4 gaps are clear of the uncertainty.
- The widest gap is in long context, where o3-pro leads 72.2 to 40.5.
- The biggest single-benchmark swing is WeirdML: 43.2% for Mercury 2 and 58.2% for o3-pro.
- Mercury 2 is cheaper at $0.25 / $0.75 per million input/output tokens, against $20 / $80 for o3-pro.
- o3-pro accepts more context: 200K tokens versus 128K.
Side by side
| Mercury 2 | o3-pro | |
|---|---|---|
| Provider | Inception | OpenAI |
| Noometry Index | 39.1 | 42.9 |
| Released | 2026-02-20 | 2025-06-10 |
| Weights | Proprietary | Proprietary |
| Context window | 128K | 200K |
| Max output | 50K | 100K |
| Input $ / M tokens | $0.25 | $20 |
| Output $ / M tokens | $0.75 | $80 |
| Results tracked | 17 | 12 |
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Category by category
Coding o3-pro leads
Mercury 2: 33.5 (#255), o3-pro: 55.5 (#24)
| Benchmark | Mercury 2 | o3-pro |
|---|---|---|
| WeirdML | 43.2% | 58.2% |
| Aider Polyglot | — | 84.9% |
| LMArena WebDev | 1171 | — |
| SciCode | 38.7% | — |
| LMArena Coding | 1391 | — |
| ALE-Bench | 785.58 | — |
Reasoning Too close to call
Mercury 2: 23.8 (#170), o3-pro: 23.8 (#171)
| Benchmark | Mercury 2 | o3-pro |
|---|---|---|
| ARC-AGI-2 | — | 4.9% |
| Kagi LLM Benchmark | — | 72.1% |
| ARC-AGI-1 | — | 59.3% |
| CritPt | 0.8% | — |
| LMArena Hard Prompts | 1362 | — |
| DTBench | — | 86.9% |
| LMCA | — | 38.5% |
| Epoch Capabilities Index | — | 147.42 |
Knowledge Mercury 2 leads
Mercury 2: 36.2 (#172), o3-pro: 29.5 (#238)
| Benchmark | Mercury 2 | o3-pro |
|---|---|---|
| Vectara Hallucination Rate | 12.3% | 23.3% |
| Confabulations | — | 14.2% |
| LMArena Expert | 1358 | — |
Multilingual Not comparable
Mercury 2: 46.6 (#157), o3-pro: —
| Benchmark | Mercury 2 | o3-pro |
|---|---|---|
| LMArena Non-English | 1331 | — |
| LMArena Chinese | 1417 | — |
| LMArena Russian | 1304 | — |
Instruction Following Not comparable
Mercury 2: 70.2 (#165), o3-pro: —
| Benchmark | Mercury 2 | o3-pro |
|---|---|---|
| LMArena Instruction Following | 1329 | — |
Long Context o3-pro leads
Mercury 2: 40.5 (#154), o3-pro: 72.2 (#1)
| Benchmark | Mercury 2 | o3-pro |
|---|---|---|
| Fiction.LiveBench | — | 97.2% |
| LMArena Longer Query | 1330 | — |
Writing & Preference o3-pro leads
Mercury 2: 53.8 (#155), o3-pro: 57.1 (#133)
| Benchmark | Mercury 2 | o3-pro |
|---|---|---|
| LMArena Text | 1355 | — |
| LMArena Creative Writing | 1289 | — |
| Short-Story Creative Writing | — | 84.4% |
| LMArena Multi-Turn | 1358 | — |
Frequently asked questions
Is Mercury 2 better than o3-pro?
o3-pro is the stronger model overall, scoring 42.9 to 39.1 on the Noometry Index. Mercury 2 costs 93× less per token, which makes it the better buy when o3-pro's lead doesn't matter for your workload.
Which is cheaper, Mercury 2 or o3-pro?
Mercury 2 is cheaper. It lists at $0.25 per million input tokens and $0.75 per million output tokens; o3-pro lists at $20 and $80.
Is Mercury 2 or o3-pro better for coding?
o3-pro scores higher on coding benchmarks: 55.5 versus 33.5 in the Noometry coding category.
Which has the bigger context window?
o3-pro does, with 200K tokens against 128K.
How many benchmarks do Mercury 2 and o3-pro share?
2 benchmarks have published results for both models. Mercury 2 has 17 scored results on Noometry and o3-pro has 12.