# GPT-5.1-Codex vs o3-mini

> GPT-5.1-Codex is the stronger model overall, scoring 38.2 to 36.7 on the Noometry Index. o3-mini costs 1.8× 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-o3-mini
- Last updated: 2026-10-10
- Shared benchmarks: 0

## Summary

- The widest gap is in agentic & tool use, where GPT-5.1-Codex leads 37.8 to 29.3.
- o3-mini is cheaper at $1.10 / $4.40 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- GPT-5.1-Codex accepts more context: 400K tokens versus 200K.

## Snapshot

| | GPT-5.1-Codex | o3-mini |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 38.2 | 36.7 |
| Rank | 178 | 205 |
| Context | 400K | 200K |
| Input $/M | $1.25 | $1.10 |
| Output $/M | $10 | $4.40 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.1-Codex: 41.7 (#107)
- o3-mini: 41.4 (#116)

| Benchmark | GPT-5.1-Codex | o3-mini |
|---|---|---|
| SWE-bench Verified (bash only) | 66% | — |
| Aider Polyglot | — | 60.4% |
| LMArena WebDev | 1337 | — |
| SciCode | — | 39.8% |
| GSO | — | 1.3% |
| WeirdML | — | 43.7% |
| LiveBench Coding | — | 82.7% |
| LMArena Coding | — | 1378 |
| CadEval | — | 54% |
| ALE-Bench | 1,245 | — |

## Agentic & Tool Use

- GPT-5.1-Codex: 37.8 (#32)
- o3-mini: 29.3 (#79)

| Benchmark | GPT-5.1-Codex | o3-mini |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| Cybench | — | 22.5% |
| METR Time Horizons | 70.8% | — |

## Reasoning

- GPT-5.1-Codex: —
- o3-mini: 16.3 (#295)

| Benchmark | GPT-5.1-Codex | o3-mini |
|---|---|---|
| ARC-AGI-2 | — | 3% |
| SimpleBench | — | 22.8% |
| ARC-AGI-1 | — | 34.5% |
| CritPt | — | 0.3% |
| Chess Puzzles | — | 17% |
| LiveBench Reasoning | — | 89.6% |
| LMArena Hard Prompts | — | 1366 |
| Mystery Game Puzzles | — | 7% |
| DTBench | — | 68.8% |
| LiveBench Data Analysis | — | 70.6% |
| LMCA | — | 19% |
| Epoch Capabilities Index | — | 140.35 |
| ForecastBench | — | 59.6 |
| LiveBench | — | 75.9% |

## Math

- GPT-5.1-Codex: 29.3 (#218)
- o3-mini: 27.6 (#236)

| Benchmark | GPT-5.1-Codex | o3-mini |
|---|---|---|
| FrontierMath (Tiers 1-3) | — | 18.6% |
| FrontierMath Tier 4 | — | 0% |
| OTIS Mock AIME 2024-2025 | — | 76.9% |
| ProofBench | 9% | — |
| LiveBench Math | — | 77.3% |
| LMArena Math | — | 1396 |
| MATH Level 5 | — | 96.5% |
| FrontierMath (Feb 2025 set) | — | 12.4% |
| FrontierMath Tier 4 (v1) | — | 4.2% |

## Knowledge

- GPT-5.1-Codex: —
- o3-mini: 38.3 (#135)

| Benchmark | GPT-5.1-Codex | o3-mini |
|---|---|---|
| GPQA Diamond | — | 77% |
| SimpleQA Verified | — | 15.3% |
| Confabulations | — | 17.9% |
| LMArena Expert | — | 1364 |

## Multilingual

- GPT-5.1-Codex: —
- o3-mini: 45.9 (#159)

| Benchmark | GPT-5.1-Codex | o3-mini |
|---|---|---|
| LMArena Non-English | — | 1319 |
| LMArena Chinese | — | 1379 |
| LMArena French | — | 1333 |
| LMArena German | — | 1303 |
| LMArena Japanese | — | 1286 |
| LMArena Korean | — | 1314 |
| LMArena Russian | — | 1304 |
| LMArena Spanish | — | 1321 |

## Instruction Following

- GPT-5.1-Codex: —
- o3-mini: 75.3 (#67)

| Benchmark | GPT-5.1-Codex | o3-mini |
|---|---|---|
| LiveBench Instruction Following | — | 84.4% |
| LMArena Instruction Following | — | 1338 |

## Long Context

- GPT-5.1-Codex: —
- o3-mini: 33.8 (#251)

| Benchmark | GPT-5.1-Codex | o3-mini |
|---|---|---|
| Fiction.LiveBench | — | 50% |
| LMArena Longer Query | — | 1343 |

## Writing & Preference

- GPT-5.1-Codex: —
- o3-mini: 50.4 (#177)

| Benchmark | GPT-5.1-Codex | o3-mini |
|---|---|---|
| LMArena Text | — | 1337 |
| LMArena Creative Writing | — | 1286 |
| Short-Story Creative Writing | — | 61.7% |
| LMArena Multi-Turn | — | 1320 |
| LiveBench Language | — | 50.7% |

## FAQ

### Is GPT-5.1-Codex better than o3-mini?

GPT-5.1-Codex is the stronger model overall, scoring 38.2 to 36.7 on the Noometry Index. o3-mini costs 1.8× 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 o3-mini?

o3-mini is cheaper. It lists at $1.10 per million input tokens and $4.40 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.

### Is GPT-5.1-Codex or o3-mini better for coding?

They score almost the same on coding (41.7 vs 41.4); test both on your own repository before choosing.

### Which has the bigger context window?

GPT-5.1-Codex does, with 400K tokens against 200K.

### How many benchmarks do GPT-5.1-Codex and o3-mini share?

0 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and o3-mini has 51.