# GPT-5.1-Codex vs Grok 4.5

> Grok 4.5 is the stronger model overall, scoring 55.0 to 38.6 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-1-codex-vs-grok-4-5
- Last updated: 2026-10-10
- Shared benchmarks: 3

## 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 60.9 to 30.3.
- 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.

## Snapshot

| | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| Provider | OpenAI | xAI |
| Noometry Index | 38.6 | 55.0 |
| Rank | 186 | 25 |
| Context | 400K | 500K |
| Input $/M | $1.25 | $2 |
| Output $/M | $10 | $6 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.1-Codex: 41.9 (#116)
- Grok 4.5: 52.2 (#35)

| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena WebDev | 1337 | 1553 |
| 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 | — | 1474 |

## Agentic & Tool Use

- GPT-5.1-Codex: 38.0 (#33)
- Grok 4.5: 44.4 (#17)

| 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

- GPT-5.1-Codex: —
- Grok 4.5: 56.1 (#25)

| 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 | — | 153.92 |

## Math

- GPT-5.1-Codex: 30.3 (#235)
- Grok 4.5: 60.9 (#35)

| 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 | — | 1459 |

## Knowledge

- GPT-5.1-Codex: —
- Grok 4.5: 62.3 (#24)

| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| GPQA Diamond | — | 93.4% |
| SimpleQA Verified | — | 48.3% |
| LMArena Expert | — | 1466 |

## Multimodal

- GPT-5.1-Codex: —
- Grok 4.5: 37.6 (#72)

| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena Vision | — | 1288 |
| Blueprint-Bench 2 | — | 27.3% |
| Furniture Assembly | — | 22.5% |
| LMArena Document | — | 1452 |

## Multilingual

- GPT-5.1-Codex: —
- Grok 4.5: 54.4 (#42)

| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena Non-English | — | 1440 |
| LMArena Chinese | — | 1496 |
| LMArena French | — | 1456 |
| LMArena German | — | 1446 |
| LMArena Japanese | — | 1428 |
| LMArena Korean | — | 1404 |
| LMArena Russian | — | 1448 |
| LMArena Spanish | — | 1450 |

## Instruction Following

- GPT-5.1-Codex: —
- Grok 4.5: 76.0 (#48)

| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena Instruction Following | — | 1446 |

## Long Context

- GPT-5.1-Codex: —
- Grok 4.5: 44.8 (#56)

| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena Longer Query | — | 1463 |

## Writing & Preference

- GPT-5.1-Codex: —
- Grok 4.5: 65.8 (#42)

| Benchmark | GPT-5.1-Codex | Grok 4.5 |
|---|---|---|
| LMArena Text | — | 1448 |
| LMArena Creative Writing | — | 1442 |
| EQ-Bench Creative Writing | — | 1579 |
| LMArena Multi-Turn | — | 1456 |

## FAQ

### Is GPT-5.1-Codex better than Grok 4.5?

Grok 4.5 is the stronger model overall, scoring 55.0 to 38.6 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: 52.2 versus 41.9 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.