Model comparison
GPT-5.1-Codex vs Grok 4.5
Grok 4.5 is the stronger model overall, scoring 55.0 to 38.2 on the Noometry Index.
Last verified . 3 shared benchmarks.
Summary
- They share 3 benchmarks with published results for both. GPT-5.1-Codex scores higher in 0 categories and Grok 4.5 in 3 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where Grok 4.5 leads 60.7 to 29.3.
- The biggest single-benchmark swing is ProofBench: 9% for GPT-5.1-Codex and 31% for Grok 4.5.
- Grok 4.5 is cheaper at $2 / $6 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- Grok 4.5 accepts more context: 500K tokens versus 400K.
Side by side
| GPT-5.1-Codex | Grok 4.5 | |
|---|---|---|
| Provider | OpenAI | xAI |
| Noometry Index | 38.2 | 55.0 |
| Released | 2025-11-12 | 2026-07-08 |
| Weights | Proprietary | Proprietary |
| Context window | 400K | 500K |
| Max output | 128K | 500K |
| Input $ / M tokens | $1.25 | $2 |
| Output $ / M tokens | $10 | $6 |
| Results tracked | 6 | 52 |
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Category by category
Coding Grok 4.5 leads
GPT-5.1-Codex: 41.7 (#107), Grok 4.5: 51.7 (#34)
| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena WebDev | 1337 | 1552 |
| ALE-Bench | 1,245 | 1,309 |
| DeepSWE | — | 53.8% |
| FrontierCode | — | 42.4% |
| SWE-bench Verified (bash only) | 66% | — |
| SciCode | — | 54.1% |
| WeirdML | — | 46.4% |
| LMArena Coding | — | 1473 |
Agentic & Tool Use Grok 4.5 leads
GPT-5.1-Codex: 37.8 (#32), Grok 4.5: 44.4 (#15)
| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| APEX-Agents | — | 56.2% |
| τ²-bench Banking | — | 47.9% |
| PostTrainBench | — | 23.4% |
| GBAEval | — | 65.4% |
| GDP.pdf | — | 14% |
| LMArena Search | — | 1213 |
| METR Time Horizons | 70.8% | — |
| Vending-Bench 2 | — | 3,887 |
Reasoning Not comparable
GPT-5.1-Codex: —, Grok 4.5: 56.0 (#23)
| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| ARC-AGI-2 | — | 52.6% |
| SimpleBench | — | 70% |
| Kagi LLM Benchmark | — | 83.5% |
| NYT Connections (extended) | — | 79.9% |
| ARC-AGI-1 | — | 87.2% |
| CritPt | — | 15.4% |
| Chess Puzzles | — | 36% |
| LMArena Hard Prompts | — | 1462 |
| DTBench | — | 96.5% |
| LMCA | — | 45.2% |
| Surface Evolver Bench | — | 74.4% |
| Epoch Capabilities Index | — | 154.02 |
Math Grok 4.5 leads
GPT-5.1-Codex: 29.3 (#218), Grok 4.5: 60.7 (#29)
| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| ProofBench | 9% | 31% |
| FrontierMath (Tiers 1-3) | — | 57.2% |
| FrontierMath Tier 4 | — | 24.4% |
| OTIS Mock AIME 2024-2025 | — | 97.8% |
| LMArena Math | — | 1457 |
Knowledge Not comparable
GPT-5.1-Codex: —, Grok 4.5: 62.3 (#21)
| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| GPQA Diamond | — | 93.4% |
| SimpleQA Verified | — | 48.3% |
| LMArena Expert | — | 1466 |
Multimodal Not comparable
GPT-5.1-Codex: —, Grok 4.5: 37.8 (#63)
| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena Vision | — | 1287 |
| Blueprint-Bench 2 | — | 27.3% |
| Furniture Assembly | — | 22.5% |
| LMArena Document | — | 1452 |
Multilingual Not comparable
GPT-5.1-Codex: —, Grok 4.5: 54.5 (#43)
| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena Non-English | — | 1439 |
| LMArena Chinese | — | 1497 |
| LMArena French | — | 1458 |
| LMArena German | — | 1448 |
| LMArena Japanese | — | 1425 |
| LMArena Korean | — | 1402 |
| LMArena Russian | — | 1447 |
| LMArena Spanish | — | 1452 |
Instruction Following Not comparable
GPT-5.1-Codex: —, Grok 4.5: 76.3 (#45)
| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena Instruction Following | — | 1446 |
Long Context Not comparable
GPT-5.1-Codex: —, Grok 4.5: 44.8 (#54)
| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena Longer Query | — | 1463 |
Writing & Preference Not comparable
GPT-5.1-Codex: —, Grok 4.5: 65.9 (#40)
| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena Text | — | 1448 |
| LMArena Creative Writing | — | 1442 |
| EQ-Bench Creative Writing | — | 1579 |
| LMArena Multi-Turn | — | 1457 |
Frequently asked questions
Is GPT-5.1-Codex better than Grok 4.5?
Grok 4.5 is the stronger model overall, scoring 55.0 to 38.2 on the Noometry Index.
Which is cheaper, GPT-5.1-Codex or Grok 4.5?
Grok 4.5 is cheaper. It lists at $2 per million input tokens and $6 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.
Is GPT-5.1-Codex or Grok 4.5 better for coding?
Grok 4.5 scores higher on coding benchmarks: 51.7 versus 41.7 in the Noometry coding category.
Which has the bigger context window?
Grok 4.5 does, with 500K tokens against 400K.
How many benchmarks do GPT-5.1-Codex and Grok 4.5 share?
3 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Grok 4.5 has 52.