# Claude Opus 5.5 vs Mercury 2

> Claude Opus 5.5 is the stronger model overall, scoring 68.5 to 38.8 on the Noometry Index. Mercury 2 costs 21× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/claude-opus-5-5-vs-mercury-2
- Last updated: 2026-10-10
- Shared benchmarks: 14

## Summary

- They share 14 benchmarks with published results for both. Claude Opus 5.5 scores higher in 7 categories and Mercury 2 in 0 categories; 7 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Claude Opus 5.5 leads 79.5 to 23.0.
- The biggest single-benchmark swing is CritPt: 31.7% for Claude Opus 5.5 and 0.8% for Mercury 2.
- Mercury 2 is cheaper at $0.25 / $0.75 per million input/output tokens, against $4 / $20 for Claude Opus 5.5.
- Claude Opus 5.5 accepts more context: 1M tokens versus 128K.

## Snapshot

| | Claude Opus 5.5 | Mercury 2 |
|---|---|---|
| Provider | Anthropic | Inception |
| Noometry Index | 68.5 | 38.8 |
| Rank | 3 | 167 |
| Context | 1M | 128K |
| Input $/M | $4 | $0.25 |
| Output $/M | $20 | $0.75 |
| Weights | Proprietary | Proprietary |

## Coding

- Claude Opus 5.5: 71.4 (#1)
- Mercury 2: 33.2 (#250)

| Benchmark | Claude Opus 5.5 | Mercury 2 |
|---|---|---|
| LMArena WebDev | 1820 | 1170 |
| SciCode | 66.9% | 38.7% |
| LMArena Coding | 1545 | 1391 |
| FrontierCode | 54.4% | — |
| CursorBench | 57.8% | — |
| FrontierSWE | 62.3% | — |
| WeirdML | — | 43.2% |
| MirrorCode | 77.4% | — |
| ALE-Bench | — | 785.58 |

## Agentic & Tool Use

- Claude Opus 5.5: 45.3 (#13)
- Mercury 2: —

| Benchmark | Claude Opus 5.5 | Mercury 2 |
|---|---|---|
| APEX-Agents | 73.5% | — |
| GDP.pdf | 30.6% | — |

## Reasoning

- Claude Opus 5.5: 79.5 (#2)
- Mercury 2: 23.0 (#170)

| Benchmark | Claude Opus 5.5 | Mercury 2 |
|---|---|---|
| CritPt | 31.7% | 0.8% |
| LMArena Hard Prompts | 1545 | 1362 |
| ARC-AGI-2 | 92.5% | — |
| NYT Connections (extended) | 88.5% | — |
| ARC-AGI-1 | 97.5% | — |
| EBR-Bench | 71.4% | — |
| Mystery Game Puzzles | 71% | — |
| DTBench | 98.9% | — |
| LMCA | 68.2% | — |

## Math

- Claude Opus 5.5: 92.4 (#2)
- Mercury 2: —

| Benchmark | Claude Opus 5.5 | Mercury 2 |
|---|---|---|
| FrontierMath (Tiers 1-3) | 91.2% | — |
| FrontierMath Tier 4 | 95% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| ProofBench | 100% | — |

## Knowledge

- Claude Opus 5.5: 66.6 (#9)
- Mercury 2: 35.6 (#170)

| Benchmark | Claude Opus 5.5 | Mercury 2 |
|---|---|---|
| LMArena Expert | 1564 | 1358 |
| GPQA Diamond | 90.6% | — |
| SimpleQA Verified | 72.2% | — |
| Vectara Hallucination Rate | — | 12.3% |

## Multimodal

- Claude Opus 5.5: 56.5 (#2)
- Mercury 2: —

| Benchmark | Claude Opus 5.5 | Mercury 2 |
|---|---|---|
| Furniture Assembly | 83.3% | — |

## Multilingual

- Claude Opus 5.5: 59.8 (#1)
- Mercury 2: 46.8 (#153)

| Benchmark | Claude Opus 5.5 | Mercury 2 |
|---|---|---|
| LMArena Non-English | 1513 | 1331 |
| LMArena Chinese | 1572 | 1416 |
| LMArena Russian | 1532 | 1303 |

## Instruction Following

- Claude Opus 5.5: 80.1 (#2)
- Mercury 2: 70.4 (#161)

| Benchmark | Claude Opus 5.5 | Mercury 2 |
|---|---|---|
| LMArena Instruction Following | 1535 | 1328 |

## Long Context

- Claude Opus 5.5: 47.3 (#18)
- Mercury 2: 40.4 (#149)

| Benchmark | Claude Opus 5.5 | Mercury 2 |
|---|---|---|
| LMArena Longer Query | 1540 | 1329 |

## Writing & Preference

- Claude Opus 5.5: 78.7 (#3)
- Mercury 2: 54.0 (#151)

| Benchmark | Claude Opus 5.5 | Mercury 2 |
|---|---|---|
| LMArena Text | 1518 | 1355 |
| LMArena Creative Writing | 1538 | 1289 |
| LMArena Multi-Turn | 1520 | 1358 |
| EQ-Bench Creative Writing | 2050 | — |

## FAQ

### Is Claude Opus 5.5 better than Mercury 2?

Claude Opus 5.5 is the stronger model overall, scoring 68.5 to 38.8 on the Noometry Index. Mercury 2 costs 21× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.

### Which is cheaper, Claude Opus 5.5 or Mercury 2?

Mercury 2 is cheaper. It lists at $0.25 per million input tokens and $0.75 per million output tokens; Claude Opus 5.5 lists at $4 and $20.

### Is Claude Opus 5.5 or Mercury 2 better for coding?

Claude Opus 5.5 scores higher on coding benchmarks: 71.4 versus 33.2 in the Noometry coding category.

### Which has the bigger context window?

Claude Opus 5.5 does, with 1M tokens against 128K.

### How many benchmarks do Claude Opus 5.5 and Mercury 2 share?

14 benchmarks have published results for both models. Claude Opus 5.5 has 35 scored results on Noometry and Mercury 2 has 17.