Model comparison
GPT-4.5 vs GPT-5.1-Codex
GPT-5.1-Codex is the stronger model overall, scoring 38.2 to 36.9 on the Noometry Index.
Last verified . 0 shared benchmarks.
Summary
- The widest gap is in agentic & tool use, where GPT-5.1-Codex leads 37.8 to 27.6.
Side by side
| GPT-4.5 | GPT-5.1-Codex | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 36.9 | 38.2 |
| Released | 2025-02-27 | 2025-11-12 |
| Weights | Proprietary | Proprietary |
| Context window | — | 400K |
| Max output | — | 128K |
| Input $ / M tokens | — | $1.25 |
| Output $ / M tokens | — | $10 |
| Results tracked | 42 | 6 |
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Category by category
Coding Too close to call
GPT-4.5: 41.8 (#102), GPT-5.1-Codex: 41.7 (#107)
| Benchmark | GPT-4.5 | GPT-5.1-Codex |
|---|---|---|
| SWE-bench Verified (bash only) | — | 66% |
| Aider Polyglot | 44.9% | — |
| LMArena WebDev | — | 1337 |
| WeirdML | 39.4% | — |
| LiveBench Coding | 75.2% | — |
| LMArena Coding | 1397 | — |
| ALE-Bench | — | 1,245 |
Agentic & Tool Use GPT-5.1-Codex leads
GPT-4.5: 27.6 (#92), GPT-5.1-Codex: 37.8 (#32)
| Benchmark | GPT-4.5 | GPT-5.1-Codex |
|---|---|---|
| Terminal-Bench | — | 60.4% |
| Cybench | 17.5% | — |
| METR Time Horizons | — | 70.8% |
Reasoning Not comparable
GPT-4.5: 14.1 (#320), GPT-5.1-Codex: —
| Benchmark | GPT-4.5 | GPT-5.1-Codex |
|---|---|---|
| ARC-AGI-2 | 0.8% | — |
| SimpleBench | 34.5% | — |
| ARC-AGI-1 | 10.3% | — |
| EnigmaEval | 3.2% | — |
| LiveBench Reasoning | 71.1% | — |
| LMArena Hard Prompts | 1404 | — |
| LiveBench Data Analysis | 64.3% | — |
| Epoch Capabilities Index | 136.74 | — |
| ForecastBench | 61.7 | — |
| LiveBench | 69% | — |
Math GPT-4.5 leads
GPT-4.5: 31.0 (#200), GPT-5.1-Codex: 29.3 (#218)
| Benchmark | GPT-4.5 | GPT-5.1-Codex |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 37.8% | — |
| ProofBench | — | 9% |
| LiveBench Math | 69.3% | — |
| LMArena Math | 1412 | — |
| MATH Level 5 | 78.6% | — |
Knowledge Not comparable
GPT-4.5: 32.4 (#205), GPT-5.1-Codex: —
| Benchmark | GPT-4.5 | GPT-5.1-Codex |
|---|---|---|
| GPQA Diamond | 68.7% | — |
| Humanity's Last Exam | 5.4% | — |
| Confabulations | 13.6% | — |
| LMArena Expert | 1394 | — |
Multimodal Not comparable
GPT-4.5: 37.0 (#68), GPT-5.1-Codex: —
| Benchmark | GPT-4.5 | GPT-5.1-Codex |
|---|---|---|
| LMArena Vision | 1195 | — |
| VPCT | 45% | — |
Multilingual Not comparable
GPT-4.5: 52.7 (#78), GPT-5.1-Codex: —
| Benchmark | GPT-4.5 | GPT-5.1-Codex |
|---|---|---|
| LMArena Non-English | 1413 | — |
| LMArena Chinese | 1421 | — |
| LMArena French | 1417 | — |
| LMArena German | 1457 | — |
| LMArena Japanese | 1416 | — |
| LMArena Korean | 1392 | — |
| LMArena Russian | 1419 | — |
Instruction Following Not comparable
GPT-4.5: 72.8 (#129), GPT-5.1-Codex: —
| Benchmark | GPT-4.5 | GPT-5.1-Codex |
|---|---|---|
| LiveBench Instruction Following | 72.3% | — |
| LMArena Instruction Following | 1404 | — |
Long Context Not comparable
GPT-4.5: 40.4 (#150), GPT-5.1-Codex: —
| Benchmark | GPT-4.5 | GPT-5.1-Codex |
|---|---|---|
| Fiction.LiveBench | 63.9% | — |
| LMArena Longer Query | 1406 | — |
Writing & Preference Not comparable
GPT-4.5: 57.1 (#129), GPT-5.1-Codex: —
| Benchmark | GPT-4.5 | GPT-5.1-Codex |
|---|---|---|
| LMArena Text | 1417 | — |
| LMArena Creative Writing | 1394 | — |
| Short-Story Creative Writing | 75.6% | — |
| EQ-Bench Creative Writing | 1258 | — |
| LMArena Multi-Turn | 1444 | — |
| LiveBench Language | 61.5% | — |
Frequently asked questions
Is GPT-4.5 better than GPT-5.1-Codex?
GPT-5.1-Codex is the stronger model overall, scoring 38.2 to 36.9 on the Noometry Index.
Is GPT-4.5 or GPT-5.1-Codex better for coding?
They score almost the same on coding (41.8 vs 41.7); test both on your own repository before choosing.
How many benchmarks do GPT-4.5 and GPT-5.1-Codex share?
0 benchmarks have published results for both models. GPT-4.5 has 42 scored results on Noometry and GPT-5.1-Codex has 6.