# GPT-5.1-Codex vs o4-mini

> o4-mini is the stronger model overall, scoring 41.6 to 38.6 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-1-codex-vs-o4-mini
- Last updated: 2026-10-11
- Shared benchmarks: 3

## Summary

- They share 3 benchmarks with published results for both. GPT-5.1-Codex scores higher in 2 categories and o4-mini in 1 category; 2 gaps are clear of the uncertainty.
- The widest gap is in math, where o4-mini leads 40.8 to 30.3.
- The biggest single-benchmark swing is SWE-bench Verified (bash only): 66% for GPT-5.1-Codex and 45% for o4-mini.
- o4-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 | o4-mini |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 38.6 | 41.6 |
| Rank | 186 | 132 |
| Context | 400K | 200K |
| Input $/M | $1.25 | $1.10 |
| Output $/M | $10 | $4.40 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.1-Codex: 41.9 (#116)
- o4-mini: 40.9 (#127)

| Benchmark | GPT-5.1-Codex | o4-mini |
|---|---|---|
| SWE-bench Verified (bash only) | 66% | 45% |
| ALE-Bench | 1,245 | 826.17 |
| Aider Polyglot | — | 72% |
| LMArena WebDev | 1337 | — |
| GSO | — | 3.6% |
| WeirdML | — | 52.6% |
| LMArena Coding | — | 1368 |
| CadEval | — | 62% |
| AlgoTune | — | 1.72 |

## Agentic & Tool Use

- GPT-5.1-Codex: 38.0 (#33)
- o4-mini: 32.6 (#61)

| Benchmark | GPT-5.1-Codex | o4-mini |
|---|---|---|
| METR Time Horizons | 70.8% | 63.9% |
| Terminal-Bench | 60.4% | — |
| Berkeley Function Calling Leaderboard | — | 53.2% |
| GDPval | — | 25.3% |

## Reasoning

- GPT-5.1-Codex: —
- o4-mini: 24.6 (#162)

| Benchmark | GPT-5.1-Codex | o4-mini |
|---|---|---|
| ARC-AGI-2 | — | 6.1% |
| SimpleBench | — | 38.7% |
| Kagi LLM Benchmark | — | 67.6% |
| ARC-AGI-1 | — | 58.7% |
| CritPt | — | 0.6% |
| Chess Puzzles | — | 26% |
| EnigmaEval | — | 9.2% |
| LMArena Hard Prompts | — | 1351 |
| Mystery Game Puzzles | — | 5% |
| DTBench | — | 77.6% |
| LMCA | — | 26.5% |
| Epoch Capabilities Index | — | 145.64 |
| ForecastBench | — | 61.8 |

## Math

- GPT-5.1-Codex: 30.3 (#235)
- o4-mini: 40.8 (#89)

| Benchmark | GPT-5.1-Codex | o4-mini |
|---|---|---|
| FrontierMath (Tiers 1-3) | — | 36.1% |
| FrontierMath Tier 4 | — | 4.9% |
| OTIS Mock AIME 2024-2025 | — | 81.7% |
| ProofBench | 9% | — |
| Omni-MATH | — | 72% |
| LMArena Math | — | 1389 |
| MATH Level 5 | — | 97.8% |
| FrontierMath (Feb 2025 set) | — | 24.8% |
| FrontierMath Tier 4 (v1) | — | 6.3% |

## Knowledge

- GPT-5.1-Codex: —
- o4-mini: 43.6 (#91)

| Benchmark | GPT-5.1-Codex | o4-mini |
|---|---|---|
| GPQA Diamond | — | 79.6% |
| Humanity's Last Exam | — | 18.1% |
| SimpleQA Verified | — | 19.6% |
| MMLU-Pro | — | 82% |
| Confabulations | — | 15.8% |
| Vectara Hallucination Rate | — | 18.6% |
| GPQA (HELM) | — | 73.5% |
| LMArena Expert | — | 1343 |

## Multimodal

- GPT-5.1-Codex: —
- o4-mini: 40.2 (#49)

| Benchmark | GPT-5.1-Codex | o4-mini |
|---|---|---|
| LMArena Vision | — | 1194 |
| GeoBench | — | 64% |
| VPCT | — | 57.5% |

## Multilingual

- GPT-5.1-Codex: —
- o4-mini: 47.0 (#154)

| Benchmark | GPT-5.1-Codex | o4-mini |
|---|---|---|
| LMArena Non-English | — | 1337 |
| LMArena Chinese | — | 1354 |
| LMArena French | — | 1364 |
| LMArena German | — | 1336 |
| LMArena Japanese | — | 1308 |
| LMArena Korean | — | 1312 |
| LMArena Russian | — | 1334 |
| LMArena Spanish | — | 1347 |

## Instruction Following

- GPT-5.1-Codex: —
- o4-mini: 75.2 (#68)

| Benchmark | GPT-5.1-Codex | o4-mini |
|---|---|---|
| IFEval | — | 92.8% |
| LMArena Instruction Following | — | 1321 |

## Long Context

- GPT-5.1-Codex: —
- o4-mini: 45.5 (#33)

| Benchmark | GPT-5.1-Codex | o4-mini |
|---|---|---|
| Fiction.LiveBench | — | 77.8% |
| LMArena Longer Query | — | 1315 |

## Writing & Preference

- GPT-5.1-Codex: —
- o4-mini: 54.0 (#152)

| Benchmark | GPT-5.1-Codex | o4-mini |
|---|---|---|
| LMArena Text | — | 1353 |
| LMArena Creative Writing | — | 1294 |
| Short-Story Creative Writing | — | 75% |
| WildBench | — | 85.4% |
| LMArena Multi-Turn | — | 1350 |

## FAQ

### Is GPT-5.1-Codex better than o4-mini?

o4-mini is the stronger model overall, scoring 41.6 to 38.6 on the Noometry Index.

### Which is cheaper, GPT-5.1-Codex or o4-mini?

o4-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 o4-mini better for coding?

They score almost the same on coding (41.9 vs 40.9); 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 o4-mini share?

3 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and o4-mini has 60.