Model comparison
Claude Opus 5.5 vs Mistral Small
Claude Opus 5.5 is the stronger model overall, scoring 68.5 to 33.1 on the Noometry Index. Mistral Small costs 30× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.
Last verified . 17 shared benchmarks.
Mistral AISummary
- They share 17 benchmarks with published results for both. Claude Opus 5.5 scores higher in 10 categories and Mistral Small in 0 categories; 10 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Opus 5.5 leads 92.4 to 15.4.
- The biggest single-benchmark swing is OTIS Mock AIME 2024-2025: 100% for Claude Opus 5.5 and 5.8% for Mistral Small.
- Mistral Small is cheaper at $0.15 / $0.60 per million input/output tokens, against $4 / $20 for Claude Opus 5.5.
- Claude Opus 5.5 accepts more context: 1M tokens versus 256K.
- Mistral Small has downloadable open weights; the other is API-only.
Side by side
| Claude Opus 5.5 | Mistral Small | |
|---|---|---|
| Provider | Anthropic | Mistral AI |
| Noometry Index | 68.5 | 33.1 |
| Released | 2026-09-22 | 2024-02-26 |
| Weights | Proprietary | Open |
| Context window | 1M | 256K |
| Max output | 128K | 256K |
| Input $ / M tokens | $4 | $0.15 |
| Output $ / M tokens | $20 | $0.60 |
| Results tracked | 35 | 39 |
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Category by category
Coding Claude Opus 5.5 leads
Claude Opus 5.5: 71.4 (#1), Mistral Small: 33.5 (#242)
| Benchmark | Claude Opus 5.5 | Mistral Small |
|---|---|---|
| SciCode | 66.9% | 26.5% |
| LMArena Coding | 1545 | 1363 |
| FrontierCode | 54.4% | — |
| CursorBench | 57.8% | — |
| LMArena WebDev | 1820 | — |
| FrontierSWE | 62.3% | — |
| BigCodeBench Instruct | — | 36.1% |
| LiveBench Coding | — | 36.2% |
| MirrorCode | 77.4% | — |
| BigCodeBench Complete | — | 46.6% |
| ALE-Bench | — | 497.62 |
Agentic & Tool Use Claude Opus 5.5 leads
Claude Opus 5.5: 45.3 (#13), Mistral Small: 27.9 (#87)
| Benchmark | Claude Opus 5.5 | Mistral Small |
|---|---|---|
| APEX-Agents | 73.5% | — |
| Berkeley Function Calling Leaderboard | — | 37.1% |
| GDP.pdf | 30.6% | — |
Reasoning Claude Opus 5.5 leads
Claude Opus 5.5: 79.5 (#2), Mistral Small: 19.3 (#238)
| Benchmark | Claude Opus 5.5 | Mistral Small |
|---|---|---|
| CritPt | 31.7% | 0% |
| LMArena Hard Prompts | 1545 | 1336 |
| DTBench | 98.9% | 70.9% |
| LMCA | 68.2% | 20.6% |
| ARC-AGI-2 | 92.5% | — |
| Kagi LLM Benchmark | — | 37.8% |
| NYT Connections (extended) | 88.5% | — |
| ARC-AGI-1 | 97.5% | — |
| EBR-Bench | 71.4% | — |
| LiveBench Reasoning | — | 44.8% |
| Mystery Game Puzzles | 71% | — |
| LiveBench Data Analysis | — | 53.7% |
| LiveBench | — | 44% |
Math Claude Opus 5.5 leads
Claude Opus 5.5: 92.4 (#2), Mistral Small: 15.4 (#287)
| Benchmark | Claude Opus 5.5 | Mistral Small |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 100% | 5.8% |
| FrontierMath (Tiers 1-3) | 91.2% | — |
| FrontierMath Tier 4 | 95% | — |
| ProofBench | 100% | — |
| LiveBench Math | — | 39.9% |
| LMArena Math | — | 1341 |
| MATH Level 5 | — | 46.8% |
Knowledge Claude Opus 5.5 leads
Claude Opus 5.5: 66.6 (#9), Mistral Small: 30.9 (#214)
| Benchmark | Claude Opus 5.5 | Mistral Small |
|---|---|---|
| GPQA Diamond | 90.6% | 47.5% |
| LMArena Expert | 1564 | 1293 |
| SimpleQA Verified | 72.2% | — |
| Vectara Hallucination Rate | — | 5.1% |
| MMLU | — | 68.7% |
Multimodal Claude Opus 5.5 leads
Claude Opus 5.5: 56.5 (#2), Mistral Small: 32.9 (#91)
| Benchmark | Claude Opus 5.5 | Mistral Small |
|---|---|---|
| LMArena Vision | — | 1142 |
| Furniture Assembly | 83.3% | — |
Multilingual Claude Opus 5.5 leads
Claude Opus 5.5: 59.8 (#1), Mistral Small: 45.7 (#164)
| Benchmark | Claude Opus 5.5 | Mistral Small |
|---|---|---|
| LMArena Non-English | 1513 | 1315 |
| LMArena Chinese | 1572 | 1342 |
| LMArena Russian | 1532 | 1324 |
| LMArena French | — | 1337 |
| LMArena German | — | 1341 |
| LMArena Japanese | — | 1275 |
| LMArena Korean | — | 1260 |
| LMArena Spanish | — | 1346 |
Instruction Following Claude Opus 5.5 leads
Claude Opus 5.5: 80.1 (#2), Mistral Small: 66.6 (#204)
| Benchmark | Claude Opus 5.5 | Mistral Small |
|---|---|---|
| LMArena Instruction Following | 1535 | 1310 |
| LiveBench Instruction Following | — | 63.7% |
Long Context Claude Opus 5.5 leads
Claude Opus 5.5: 47.3 (#18), Mistral Small: 40.4 (#151)
| Benchmark | Claude Opus 5.5 | Mistral Small |
|---|---|---|
| LMArena Longer Query | 1540 | 1327 |
Writing & Preference Claude Opus 5.5 leads
Claude Opus 5.5: 78.7 (#3), Mistral Small: 52.6 (#165)
| Benchmark | Claude Opus 5.5 | Mistral Small |
|---|---|---|
| LMArena Text | 1518 | 1338 |
| LMArena Creative Writing | 1538 | 1304 |
| LMArena Multi-Turn | 1520 | 1344 |
| EQ-Bench Creative Writing | 2050 | — |
| LiveBench Language | — | 30.5% |
Frequently asked questions
Is Claude Opus 5.5 better than Mistral Small?
Claude Opus 5.5 is the stronger model overall, scoring 68.5 to 33.1 on the Noometry Index. Mistral Small costs 30× 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 Mistral Small?
Mistral Small is cheaper. It lists at $0.15 per million input tokens and $0.60 per million output tokens; Claude Opus 5.5 lists at $4 and $20.
Is Claude Opus 5.5 or Mistral Small better for coding?
Claude Opus 5.5 scores higher on coding benchmarks: 71.4 versus 33.5 in the Noometry coding category.
Which has the bigger context window?
Claude Opus 5.5 does, with 1M tokens against 256K.
How many benchmarks do Claude Opus 5.5 and Mistral Small share?
17 benchmarks have published results for both models. Claude Opus 5.5 has 35 scored results on Noometry and Mistral Small has 39.