# GPT-5.5 Pro vs Mistral Small 3.1

> GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 31.7 on the Noometry Index. Mistral Small 3.1 costs 168× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/gpt-5-5-pro-vs-mistral-small-3-1
- Last updated: 2026-10-12
- Shared benchmarks: 4

## Summary

- They share 4 benchmarks with published results for both. GPT-5.5 Pro scores higher in 3 categories and Mistral Small 3.1 in 0 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-5.5 Pro leads 84.0 to 14.7.
- The biggest single-benchmark swing is OTIS Mock AIME 2024-2025: 100% for GPT-5.5 Pro and 3.9% for Mistral Small 3.1.
- Mistral Small 3.1 is cheaper at $0.35 / $0.56 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.
- GPT-5.5 Pro accepts more context: 1.05M tokens versus 128K.
- Mistral Small 3.1 has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| Provider | OpenAI | Mistral AI |
| Noometry Index | 64.3 | 31.7 |
| Rank | 8 | 269 |
| Context | 1.05M | 128K |
| Input $/M | $30 | $0.35 |
| Output $/M | $180 | $0.56 |
| Weights | Proprietary | Open |

## Coding

- GPT-5.5 Pro: —
- Mistral Small 3.1: 38.3 (#179)

| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| LMArena Coding | — | 1309 |

## Reasoning

- GPT-5.5 Pro: 73.3 (#10)
- Mistral Small 3.1: 19.7 (#254)

| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| Chess Puzzles | 64% | 1% |
| Epoch Capabilities Index | 162.07 | 127.48 |
| ARC-AGI-2 | 84.6% | — |
| SimpleBench | 76.9% | — |
| ARC-AGI-1 | 96.5% | — |
| CritPt | 30.6% | — |
| LMArena Hard Prompts | — | 1278 |
| DTBench | 96% | — |
| LMCA | 53.9% | — |

## Math

- GPT-5.5 Pro: 84.0 (#10)
- Mistral Small 3.1: 14.7 (#301)

| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 100% | 3.9% |
| FrontierMath (Tiers 1-3) | 87.7% | — |
| FrontierMath Tier 4 | 78% | — |
| Omni-MATH | — | 24.8% |
| LMArena Math | — | 1262 |
| FrontierMath (Feb 2025 set) | 52.4% | — |
| FrontierMath Tier 4 (v1) | 39.6% | — |

## Knowledge

- GPT-5.5 Pro: 64.1 (#19)
- Mistral Small 3.1: 22.6 (#271)

| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| GPQA Diamond | 93.9% | 41.9% |
| MMLU-Pro | — | 61% |
| GPQA (HELM) | — | 39.2% |
| LMArena Expert | — | 1257 |

## Multimodal

- GPT-5.5 Pro: —
- Mistral Small 3.1: 33.2 (#99)

| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| LMArena Vision | — | 1136 |

## Multilingual

- GPT-5.5 Pro: —
- Mistral Small 3.1: 41.2 (#209)

| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| LMArena Non-English | — | 1255 |
| LMArena Chinese | — | 1253 |
| LMArena French | — | 1273 |
| LMArena German | — | 1266 |
| LMArena Japanese | — | 1208 |
| LMArena Korean | — | 1206 |
| LMArena Russian | — | 1263 |
| LMArena Spanish | — | 1283 |

## Instruction Following

- GPT-5.5 Pro: —
- Mistral Small 3.1: 63.6 (#230)

| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| IFEval | — | 75% |
| LMArena Instruction Following | — | 1264 |

## Long Context

- GPT-5.5 Pro: —
- Mistral Small 3.1: 39.5 (#178)

| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| LMArena Longer Query | — | 1299 |

## Writing & Preference

- GPT-5.5 Pro: —
- Mistral Small 3.1: 37.0 (#259)

| Benchmark | GPT-5.5 Pro | Mistral Small 3.1 |
|---|---|---|
| LMArena Text | — | 1277 |
| LMArena Creative Writing | — | 1253 |
| EQ-Bench Creative Writing | — | 761 |
| WildBench | — | 78.8% |
| LMArena Multi-Turn | — | 1270 |

## FAQ

### Is GPT-5.5 Pro better than Mistral Small 3.1?

GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 31.7 on the Noometry Index. Mistral Small 3.1 costs 168× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.

### Which is cheaper, GPT-5.5 Pro or Mistral Small 3.1?

Mistral Small 3.1 is cheaper. It lists at $0.35 per million input tokens and $0.56 per million output tokens; GPT-5.5 Pro lists at $30 and $180.

### Which has the bigger context window?

GPT-5.5 Pro does, with 1.05M tokens against 128K.

### How many benchmarks do GPT-5.5 Pro and Mistral Small 3.1 share?

4 benchmarks have published results for both models. GPT-5.5 Pro has 14 scored results on Noometry and Mistral Small 3.1 has 28.