Model comparison
Claude Sonnet 5 vs GPT-5.1-Codex
Claude Sonnet 5 is the stronger model overall, scoring 54.5 to 38.2 on the Noometry Index.
Last verified . 3 shared benchmarks.
Summary
- They share 3 benchmarks with published results for both. Claude Sonnet 5 scores higher in 3 categories and GPT-5.1-Codex in 0 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Sonnet 5 leads 66.1 to 29.3.
- The biggest single-benchmark swing is ProofBench: 77% for Claude Sonnet 5 and 9% for GPT-5.1-Codex.
- GPT-5.1-Codex is cheaper at $1.25 / $10 per million input/output tokens, against $2 / $10 for Claude Sonnet 5.
- Claude Sonnet 5 accepts more context: 1M tokens versus 400K.
Side by side
| Claude Sonnet 5 | GPT-5.1-Codex | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Noometry Index | 54.5 | 38.2 |
| Released | 2026-06-29 | 2025-11-12 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 400K |
| Max output | 128K | 128K |
| Input $ / M tokens | $2 | $1.25 |
| Output $ / M tokens | $10 | $10 |
| Results tracked | 51 | 6 |
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Category by category
Coding Claude Sonnet 5 leads
Claude Sonnet 5: 55.5 (#20), GPT-5.1-Codex: 41.7 (#107)
| Benchmark | Claude Sonnet 5 | GPT-5.1-Codex |
|---|---|---|
| LMArena WebDev | 1540 | 1337 |
| ALE-Bench | 1,463 | 1,245 |
| DeepSWE | 53.8% | — |
| FrontierCode | 42.7% | — |
| SWE-bench Verified (bash only) | — | 66% |
| CursorBench | 34.1% | — |
| SciCode | 53.6% | — |
| GSO | 37.3% | — |
| WeirdML | 68.8% | — |
| LMArena Coding | 1483 | — |
Agentic & Tool Use Claude Sonnet 5 leads
Claude Sonnet 5: 42.7 (#16), GPT-5.1-Codex: 37.8 (#32)
| Benchmark | Claude Sonnet 5 | GPT-5.1-Codex |
|---|---|---|
| Terminal-Bench | — | 60.4% |
| APEX-Agents | 54.5% | — |
| GBAEval | 65.3% | — |
| LMArena Search | 1194 | — |
| METR Time Horizons | — | 70.8% |
| Vending-Bench 2 | 6,378 | — |
Reasoning Not comparable
Claude Sonnet 5: 48.2 (#37), GPT-5.1-Codex: —
| Benchmark | Claude Sonnet 5 | GPT-5.1-Codex |
|---|---|---|
| SimpleBench | 60.6% | — |
| NYT Connections (extended) | 75.1% | — |
| CritPt | 16.9% | — |
| Chess Puzzles | 35% | — |
| LMArena Hard Prompts | 1461 | — |
| Mystery Game Puzzles | 35% | — |
| DTBench | 92.5% | — |
| LMCA | 50% | — |
| Surface Evolver Bench | 60% | — |
| Bench to the Future 3 | 0.14 | — |
| Epoch Capabilities Index | 156.34 | — |
| ForecastBench | 61.1 | — |
Math Claude Sonnet 5 leads
Claude Sonnet 5: 66.1 (#21), GPT-5.1-Codex: 29.3 (#218)
| Benchmark | Claude Sonnet 5 | GPT-5.1-Codex |
|---|---|---|
| ProofBench | 77% | 9% |
| FrontierMath (Tiers 1-3) | 65.6% | — |
| FrontierMath Tier 4 | 29.3% | — |
| OTIS Mock AIME 2024-2025 | 94.7% | — |
| LMArena Math | 1467 | — |
Knowledge Not comparable
Claude Sonnet 5: 55.7 (#42), GPT-5.1-Codex: —
| Benchmark | Claude Sonnet 5 | GPT-5.1-Codex |
|---|---|---|
| GPQA Diamond | 90.5% | — |
| SimpleQA Verified | 33.7% | — |
| LMArena Expert | 1491 | — |
Multimodal Not comparable
Claude Sonnet 5: 42.4 (#26), GPT-5.1-Codex: —
| Benchmark | Claude Sonnet 5 | GPT-5.1-Codex |
|---|---|---|
| LMArena Vision | 1275 | — |
| Blueprint-Bench 2 | 24.9% | — |
| LMArena Document | 1466 | — |
Multilingual Not comparable
Claude Sonnet 5: 54.0 (#55), GPT-5.1-Codex: —
| Benchmark | Claude Sonnet 5 | GPT-5.1-Codex |
|---|---|---|
| LMArena Non-English | 1431 | — |
| LMArena Chinese | 1475 | — |
| LMArena French | 1457 | — |
| LMArena German | 1448 | — |
| LMArena Japanese | 1422 | — |
| LMArena Korean | 1411 | — |
| LMArena Russian | 1452 | — |
| LMArena Spanish | 1436 | — |
Instruction Following Not comparable
Claude Sonnet 5: 76.6 (#39), GPT-5.1-Codex: —
| Benchmark | Claude Sonnet 5 | GPT-5.1-Codex |
|---|---|---|
| LMArena Instruction Following | 1453 | — |
Long Context Not comparable
Claude Sonnet 5: 44.8 (#53), GPT-5.1-Codex: —
| Benchmark | Claude Sonnet 5 | GPT-5.1-Codex |
|---|---|---|
| LMArena Longer Query | 1464 | — |
Writing & Preference Not comparable
Claude Sonnet 5: 69.4 (#24), GPT-5.1-Codex: —
| Benchmark | Claude Sonnet 5 | GPT-5.1-Codex |
|---|---|---|
| LMArena Text | 1443 | — |
| LMArena Creative Writing | 1416 | — |
| EQ-Bench Creative Writing | 1794 | — |
| EQ-Bench 4 | 1236 | — |
| LMArena Multi-Turn | 1454 | — |
Frequently asked questions
Is Claude Sonnet 5 better than GPT-5.1-Codex?
Claude Sonnet 5 is the stronger model overall, scoring 54.5 to 38.2 on the Noometry Index.
Which is cheaper, Claude Sonnet 5 or GPT-5.1-Codex?
GPT-5.1-Codex is cheaper. It lists at $1.25 per million input tokens and $10 per million output tokens; Claude Sonnet 5 lists at $2 and $10.
Is Claude Sonnet 5 or GPT-5.1-Codex better for coding?
Claude Sonnet 5 scores higher on coding benchmarks: 55.5 versus 41.7 in the Noometry coding category.
Which has the bigger context window?
Claude Sonnet 5 does, with 1M tokens against 400K.
How many benchmarks do Claude Sonnet 5 and GPT-5.1-Codex share?
3 benchmarks have published results for both models. Claude Sonnet 5 has 51 scored results on Noometry and GPT-5.1-Codex has 6.