Model comparison
Claude Sonnet 5.5 vs o3
Claude Sonnet 5.5 is the stronger model overall, scoring 61.9 to 47.5 on the Noometry Index.
Last verified . 21 shared benchmarks.
Summary
- They share 21 benchmarks with published results for both. Claude Sonnet 5.5 scores higher in 9 categories and o3 in 1 category; 10 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Sonnet 5.5 leads 87.9 to 50.2.
- The biggest single-benchmark swing is FrontierMath (Tiers 1-3): 88.8% for Claude Sonnet 5.5 and 33.3% for o3.
- o3 is cheaper at $2 / $8 per million input/output tokens, against $2 / $10 for Claude Sonnet 5.5.
- Claude Sonnet 5.5 accepts more context: 1M tokens versus 200K.
Side by side
| Claude Sonnet 5.5 | o3 | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Noometry Index | 61.9 | 47.5 |
| Released | 2026-09-28 | 2025-04-16 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 200K |
| Max output | 128K | 100K |
| Input $ / M tokens | $2 | $2 |
| Output $ / M tokens | $10 | $8 |
| Results tracked | 32 | 63 |
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Category by category
Coding Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 67.3 (#6), o3: 46.8 (#64)
| Benchmark | Claude Sonnet 5.5 | o3 |
|---|---|---|
| LMArena Coding | 1513 | 1408 |
| ALE-Bench | 1,819 | 933.55 |
| SWE-bench Verified | — | 62.3% |
| FrontierCode | 52.1% | — |
| SWE-bench Verified (bash only) | — | 58.4% |
| Aider Polyglot | — | 81.3% |
| CursorBench | 55.5% | — |
| LMArena WebDev | 1774 | — |
| FrontierSWE | 61.9% | — |
| SciCode | 61% | — |
| GSO | — | 8.8% |
| WeirdML | — | 52.4% |
| CadEval | — | 74% |
Agentic & Tool Use Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 45.0 (#16), o3: 34.5 (#44)
| Benchmark | Claude Sonnet 5.5 | o3 |
|---|---|---|
| APEX-Agents | 75.5% | — |
| Berkeley Function Calling Leaderboard | — | 63% |
| GDPval | — | 30.8% |
| DeepResearch Bench | — | 45.2% |
| OSWorld | — | 23% |
| LMArena Search | — | 1144 |
| METR Time Horizons | — | 65.4% |
Reasoning Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 54.0 (#28), o3: 32.0 (#78)
| Benchmark | Claude Sonnet 5.5 | o3 |
|---|---|---|
| CritPt | 31.4% | 1.4% |
| LMArena Hard Prompts | 1495 | 1402 |
| Mystery Game Puzzles | 65% | 29% |
| Epoch Capabilities Index | 165.03 | 146.86 |
| ARC-AGI-2 | — | 6.5% |
| SimpleBench | — | 53.1% |
| Kagi LLM Benchmark | — | 67.6% |
| NYT Connections (extended) | 80.5% | — |
| ARC-AGI-1 | — | 60.8% |
| Chess Puzzles | — | 38% |
| EnigmaEval | — | 13.1% |
| DTBench | — | 84.8% |
| LMCA | — | 39.7% |
| ForecastBench | — | 62.5 |
Math Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 87.9 (#6), o3: 50.2 (#58)
| Benchmark | Claude Sonnet 5.5 | o3 |
|---|---|---|
| FrontierMath (Tiers 1-3) | 88.8% | 33.3% |
| OTIS Mock AIME 2024-2025 | 100% | 84.4% |
| LMArena Math | 1510 | 1426 |
| FrontierMath Tier 4 | 80.5% | — |
| ProofBench | 100% | — |
| Omni-MATH | — | 71.4% |
| MATH Level 5 | — | 97.8% |
| FrontierMath (Feb 2025 set) | — | 18.7% |
| FrontierMath Erdős | 2.9% | — |
| FrontierMath Tier 4 (v1) | — | 2.1% |
Knowledge Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 66.0 (#12), o3: 54.6 (#52)
| Benchmark | Claude Sonnet 5.5 | o3 |
|---|---|---|
| GPQA Diamond | 95.6% | 81.8% |
| SimpleQA Verified | 46.5% | 49.4% |
| LMArena Expert | 1540 | 1402 |
| Humanity's Last Exam | — | 20.3% |
| MMLU-Pro | — | 85.9% |
| Confabulations | — | 14.4% |
| GPQA (HELM) | — | 75.3% |
Multimodal Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 51.5 (#6), o3: 41.4 (#36)
| Benchmark | Claude Sonnet 5.5 | o3 |
|---|---|---|
| LMArena Vision | 1289 | 1214 |
| GeoBench | — | 74% |
| VPCT | — | 52% |
| Furniture Assembly | 75% | — |
Multilingual Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 55.3 (#30), o3: 51.7 (#105)
| Benchmark | Claude Sonnet 5.5 | o3 |
|---|---|---|
| LMArena Non-English | 1452 | 1401 |
| LMArena Chinese | 1522 | 1437 |
| LMArena Russian | 1451 | 1406 |
| LMArena French | — | 1430 |
| LMArena German | — | 1420 |
| LMArena Japanese | — | 1403 |
| LMArena Korean | — | 1370 |
| LMArena Spanish | — | 1395 |
Instruction Following Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 78.3 (#11), o3: 72.8 (#127)
| Benchmark | Claude Sonnet 5.5 | o3 |
|---|---|---|
| LMArena Instruction Following | 1495 | 1368 |
| IFEval | — | 86.9% |
Long Context o3 leads
Claude Sonnet 5.5: 45.9 (#28), o3: 53.3 (#6)
| Benchmark | Claude Sonnet 5.5 | o3 |
|---|---|---|
| LMArena Longer Query | 1498 | 1372 |
| Fiction.LiveBench | — | 88.9% |
| CL-bench | — | 17.8% |
Writing & Preference Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 66.0 (#40), o3: 63.5 (#64)
| Benchmark | Claude Sonnet 5.5 | o3 |
|---|---|---|
| LMArena Text | 1471 | 1410 |
| LMArena Creative Writing | 1465 | 1359 |
| LMArena Multi-Turn | 1474 | 1405 |
| Short-Story Creative Writing | — | 83.9% |
| EQ-Bench Creative Writing | — | 1676 |
| WildBench | — | 86.1% |
Frequently asked questions
Is Claude Sonnet 5.5 better than o3?
Claude Sonnet 5.5 is the stronger model overall, scoring 61.9 to 47.5 on the Noometry Index.
Which is cheaper, Claude Sonnet 5.5 or o3?
o3 is cheaper. It lists at $2 per million input tokens and $8 per million output tokens; Claude Sonnet 5.5 lists at $2 and $10.
Is Claude Sonnet 5.5 or o3 better for coding?
Claude Sonnet 5.5 scores higher on coding benchmarks: 67.3 versus 46.8 in the Noometry coding category.
Which has the bigger context window?
Claude Sonnet 5.5 does, with 1M tokens against 200K.
How many benchmarks do Claude Sonnet 5.5 and o3 share?
21 benchmarks have published results for both models. Claude Sonnet 5.5 has 32 scored results on Noometry and o3 has 63.