# GPT-5.1-Codex vs Phi 3 Small 8k Instruct

> GPT-5.1-Codex is the stronger model overall, scoring 38.6 to 29.3 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-1-codex-vs-phi-3-small-8k-instruct
- Last updated: 2026-10-11
- Shared benchmarks: 0

## Summary

- The widest gap is in coding, where GPT-5.1-Codex leads 41.9 to 27.9.
- Phi 3 Small 8k Instruct has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.1-Codex | Phi 3 Small 8k Instruct |
|---|---|---|
| Provider | OpenAI | Microsoft |
| Noometry Index | 38.6 | 29.3 |
| Rank | 186 | 314 |
| Context | 400K | — |
| Input $/M | $1.25 | — |
| Output $/M | $10 | — |
| Weights | Proprietary | Open |

## Coding

- GPT-5.1-Codex: 41.9 (#116)
- Phi 3 Small 8k Instruct: 27.9 (#318)

| Benchmark | GPT-5.1-Codex | Phi 3 Small 8k Instruct |
|---|---|---|
| SWE-bench Verified (bash only) | 66% | — |
| LMArena WebDev | 1337 | — |
| LiveBench Coding | — | 20.3% |
| LMArena Coding | — | 1101 |
| ALE-Bench | 1,245 | — |

## Agentic & Tool Use

- GPT-5.1-Codex: 38.0 (#33)
- Phi 3 Small 8k Instruct: —

| Benchmark | GPT-5.1-Codex | Phi 3 Small 8k Instruct |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| METR Time Horizons | 70.8% | — |

## Reasoning

- GPT-5.1-Codex: —
- Phi 3 Small 8k Instruct: 14.8 (#323)

| Benchmark | GPT-5.1-Codex | Phi 3 Small 8k Instruct |
|---|---|---|
| LiveBench Reasoning | — | 15.9% |
| LMArena Hard Prompts | — | 1100 |
| LiveBench Data Analysis | — | 30.3% |
| Adversarial NLI | — | 58.1% |
| BIG-Bench Hard | — | 79.1% |
| HellaSwag | — | 77% |
| LiveBench | — | 24% |
| WinoGrande | — | 81.5% |

## Math

- GPT-5.1-Codex: 30.3 (#235)
- Phi 3 Small 8k Instruct: 27.6 (#248)

| Benchmark | GPT-5.1-Codex | Phi 3 Small 8k Instruct |
|---|---|---|
| ProofBench | 9% | — |
| LiveBench Math | — | 17.6% |
| LMArena Math | — | 1151 |

## Knowledge

- GPT-5.1-Codex: —
- Phi 3 Small 8k Instruct: 29.1 (#240)

| Benchmark | GPT-5.1-Codex | Phi 3 Small 8k Instruct |
|---|---|---|
| LMArena Expert | — | 1067 |
| ARC (AI2) Challenge | — | 90.7% |
| MMLU | — | 75.7% |
| OpenBookQA | — | 88% |
| TriviaQA | — | 58.1% |

## Multilingual

- GPT-5.1-Codex: —
- Phi 3 Small 8k Instruct: 28.5 (#272)

| Benchmark | GPT-5.1-Codex | Phi 3 Small 8k Instruct |
|---|---|---|
| LMArena Non-English | — | 1058 |
| LMArena Chinese | — | 1061 |
| LMArena French | — | 1135 |
| LMArena German | — | 1080 |
| LMArena Japanese | — | 966 |
| LMArena Korean | — | 894 |
| LMArena Russian | — | 1111 |
| LMArena Spanish | — | 1111 |

## Instruction Following

- GPT-5.1-Codex: —
- Phi 3 Small 8k Instruct: 51.9 (#292)

| Benchmark | GPT-5.1-Codex | Phi 3 Small 8k Instruct |
|---|---|---|
| LiveBench Instruction Following | — | 47.2% |
| LMArena Instruction Following | — | 1087 |

## Long Context

- GPT-5.1-Codex: —
- Phi 3 Small 8k Instruct: 33.0 (#267)

| Benchmark | GPT-5.1-Codex | Phi 3 Small 8k Instruct |
|---|---|---|
| LMArena Longer Query | — | 1088 |

## Writing & Preference

- GPT-5.1-Codex: —
- Phi 3 Small 8k Instruct: 31.1 (#284)

| Benchmark | GPT-5.1-Codex | Phi 3 Small 8k Instruct |
|---|---|---|
| LMArena Text | — | 1110 |
| LMArena Creative Writing | — | 1083 |
| LMArena Multi-Turn | — | 1068 |
| LiveBench Language | — | 12.9% |

## FAQ

### Is GPT-5.1-Codex better than Phi 3 Small 8k Instruct?

GPT-5.1-Codex is the stronger model overall, scoring 38.6 to 29.3 on the Noometry Index.

### Is GPT-5.1-Codex or Phi 3 Small 8k Instruct better for coding?

GPT-5.1-Codex scores higher on coding benchmarks: 41.9 versus 27.9 in the Noometry coding category.

### How many benchmarks do GPT-5.1-Codex and Phi 3 Small 8k Instruct share?

0 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Phi 3 Small 8k Instruct has 32.