# GPT-5.1-Codex vs Mistral Small

> GPT-5.1-Codex is the stronger model overall, scoring 38.2 to 33.1 on the Noometry Index. Mistral Small costs 13× less per token, which makes it the better buy when GPT-5.1-Codex's lead doesn't matter for your workload.

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

## Summary

- They share 1 benchmark with published results for both. GPT-5.1-Codex scores higher in 3 categories and Mistral Small in 0 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-5.1-Codex leads 29.3 to 15.4.
- Mistral Small is cheaper at $0.15 / $0.60 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- GPT-5.1-Codex accepts more context: 400K tokens versus 256K.
- Mistral Small has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.1-Codex | Mistral Small |
|---|---|---|
| Provider | OpenAI | Mistral AI |
| Noometry Index | 38.2 | 33.1 |
| Rank | 178 | 238 |
| Context | 400K | 256K |
| Input $/M | $1.25 | $0.15 |
| Output $/M | $10 | $0.60 |
| Weights | Proprietary | Open |

## Coding

- GPT-5.1-Codex: 41.7 (#107)
- Mistral Small: 33.5 (#242)

| Benchmark | GPT-5.1-Codex | Mistral Small |
|---|---|---|
| ALE-Bench | 1,245 | 497.62 |
| SWE-bench Verified (bash only) | 66% | — |
| LMArena WebDev | 1337 | — |
| SciCode | — | 26.5% |
| BigCodeBench Instruct | — | 36.1% |
| LiveBench Coding | — | 36.2% |
| LMArena Coding | — | 1363 |
| BigCodeBench Complete | — | 46.6% |

## Agentic & Tool Use

- GPT-5.1-Codex: 37.8 (#32)
- Mistral Small: 27.9 (#87)

| Benchmark | GPT-5.1-Codex | Mistral Small |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| Berkeley Function Calling Leaderboard | — | 37.1% |
| METR Time Horizons | 70.8% | — |

## Reasoning

- GPT-5.1-Codex: —
- Mistral Small: 19.3 (#238)

| Benchmark | GPT-5.1-Codex | Mistral Small |
|---|---|---|
| Kagi LLM Benchmark | — | 37.8% |
| CritPt | — | 0% |
| LiveBench Reasoning | — | 44.8% |
| LMArena Hard Prompts | — | 1336 |
| DTBench | — | 70.9% |
| LiveBench Data Analysis | — | 53.7% |
| LMCA | — | 20.6% |
| LiveBench | — | 44% |

## Math

- GPT-5.1-Codex: 29.3 (#218)
- Mistral Small: 15.4 (#287)

| Benchmark | GPT-5.1-Codex | Mistral Small |
|---|---|---|
| OTIS Mock AIME 2024-2025 | — | 5.8% |
| ProofBench | 9% | — |
| LiveBench Math | — | 39.9% |
| LMArena Math | — | 1341 |
| MATH Level 5 | — | 46.8% |

## Knowledge

- GPT-5.1-Codex: —
- Mistral Small: 30.9 (#214)

| Benchmark | GPT-5.1-Codex | Mistral Small |
|---|---|---|
| GPQA Diamond | — | 47.5% |
| Vectara Hallucination Rate | — | 5.1% |
| LMArena Expert | — | 1293 |
| MMLU | — | 68.7% |

## Multimodal

- GPT-5.1-Codex: —
- Mistral Small: 32.9 (#91)

| Benchmark | GPT-5.1-Codex | Mistral Small |
|---|---|---|
| LMArena Vision | — | 1142 |

## Multilingual

- GPT-5.1-Codex: —
- Mistral Small: 45.7 (#164)

| Benchmark | GPT-5.1-Codex | Mistral Small |
|---|---|---|
| LMArena Non-English | — | 1315 |
| LMArena Chinese | — | 1342 |
| LMArena French | — | 1337 |
| LMArena German | — | 1341 |
| LMArena Japanese | — | 1275 |
| LMArena Korean | — | 1260 |
| LMArena Russian | — | 1324 |
| LMArena Spanish | — | 1346 |

## Instruction Following

- GPT-5.1-Codex: —
- Mistral Small: 66.6 (#204)

| Benchmark | GPT-5.1-Codex | Mistral Small |
|---|---|---|
| LiveBench Instruction Following | — | 63.7% |
| LMArena Instruction Following | — | 1310 |

## Long Context

- GPT-5.1-Codex: —
- Mistral Small: 40.4 (#151)

| Benchmark | GPT-5.1-Codex | Mistral Small |
|---|---|---|
| LMArena Longer Query | — | 1327 |

## Writing & Preference

- GPT-5.1-Codex: —
- Mistral Small: 52.6 (#165)

| Benchmark | GPT-5.1-Codex | Mistral Small |
|---|---|---|
| LMArena Text | — | 1338 |
| LMArena Creative Writing | — | 1304 |
| LMArena Multi-Turn | — | 1344 |
| LiveBench Language | — | 30.5% |

## FAQ

### Is GPT-5.1-Codex better than Mistral Small?

GPT-5.1-Codex is the stronger model overall, scoring 38.2 to 33.1 on the Noometry Index. Mistral Small costs 13× less per token, which makes it the better buy when GPT-5.1-Codex's lead doesn't matter for your workload.

### Which is cheaper, GPT-5.1-Codex or Mistral Small?

Mistral Small is cheaper. It lists at $0.15 per million input tokens and $0.60 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.

### Is GPT-5.1-Codex or Mistral Small better for coding?

GPT-5.1-Codex scores higher on coding benchmarks: 41.7 versus 33.5 in the Noometry coding category.

### Which has the bigger context window?

GPT-5.1-Codex does, with 400K tokens against 256K.

### How many benchmarks do GPT-5.1-Codex and Mistral Small share?

1 benchmark has published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Mistral Small has 39.