# GPT-5.1-Codex vs GPT-6 Astra

> GPT-6 Astra is the stronger model overall, scoring 70.3 to 38.2 on the Noometry Index. GPT-5.1-Codex costs 5.8× less per token, which makes it the better buy when GPT-6 Astra's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/gpt-5-1-codex-vs-gpt-6-astra
- Last updated: 2026-10-10
- Shared benchmarks: 3

## Summary

- They share 3 benchmarks with published results for both. GPT-5.1-Codex scores higher in 0 categories and GPT-6 Astra in 3 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-6 Astra leads 93.4 to 29.3.
- The biggest single-benchmark swing is ProofBench: 9% for GPT-5.1-Codex and 99% for GPT-6 Astra.
- GPT-5.1-Codex is cheaper at $1.25 / $10 per million input/output tokens, against $10 / $50 for GPT-6 Astra.
- GPT-6 Astra accepts more context: 1.05M tokens versus 400K.

## Snapshot

| | GPT-5.1-Codex | GPT-6 Astra |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 38.2 | 70.3 |
| Rank | 178 | 1 |
| Context | 400K | 1.05M |
| Input $/M | $1.25 | $10 |
| Output $/M | $10 | $50 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.1-Codex: 41.7 (#107)
- GPT-6 Astra: 70.5 (#3)

| Benchmark | GPT-5.1-Codex | GPT-6 Astra |
|---|---|---|
| LMArena WebDev | 1337 | 1792 |
| ALE-Bench | 1,245 | 2,951 |
| DeepSWE | — | 74.1% |
| FrontierCode | — | 53.3% |
| SWE-bench Verified (bash only) | 66% | — |
| FrontierSWE | — | 65.5% |
| SciCode | — | 56.5% |
| WeirdML | — | 93.6% |
| LMArena Coding | — | 1488 |
| MirrorCode | — | 46.7% |

## Agentic & Tool Use

- GPT-5.1-Codex: 37.8 (#32)
- GPT-6 Astra: 52.3 (#3)

| Benchmark | GPT-5.1-Codex | GPT-6 Astra |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| APEX-Agents | — | 64.7% |
| Remote Labor Index | — | 20.8% |
| BALROG | — | 68.3% |
| METR Time Horizons | 70.8% | — |
| Vending-Bench 2 | — | 15,515 |

## Reasoning

- GPT-5.1-Codex: —
- GPT-6 Astra: 85.1 (#1)

| Benchmark | GPT-5.1-Codex | GPT-6 Astra |
|---|---|---|
| ARC-AGI-2 | — | 95% |
| NYT Connections (extended) | — | 98.1% |
| ARC-AGI-1 | — | 98.5% |
| CritPt | — | 31.7% |
| Chess Puzzles | — | 72% |
| EBR-Bench | — | 76.2% |
| LMArena Hard Prompts | — | 1464 |
| Mystery Game Puzzles | — | 84% |
| DTBench | — | 97.3% |
| LMCA | — | 64.4% |
| Bench to the Future 3 | — | 0.14 |
| Epoch Capabilities Index | — | 166.6 |

## Math

- GPT-5.1-Codex: 29.3 (#218)
- GPT-6 Astra: 93.4 (#1)

| Benchmark | GPT-5.1-Codex | GPT-6 Astra |
|---|---|---|
| ProofBench | 9% | 99% |
| FrontierMath (Tiers 1-3) | — | 93.7% |
| FrontierMath Tier 4 | — | 97.6% |
| OTIS Mock AIME 2024-2025 | — | 100% |
| LMArena Math | — | 1463 |
| FrontierMath Erdős | — | 2.9% |

## Knowledge

- GPT-5.1-Codex: —
- GPT-6 Astra: 75.3 (#1)

| Benchmark | GPT-5.1-Codex | GPT-6 Astra |
|---|---|---|
| GPQA Diamond | — | 95.8% |
| Humanity's Last Exam | — | 54.8% |
| SimpleQA Verified | — | 75.6% |
| Vectara Hallucination Rate | — | 8.7% |
| LMArena Expert | — | 1486 |

## Multimodal

- GPT-5.1-Codex: —
- GPT-6 Astra: 55.1 (#3)

| Benchmark | GPT-5.1-Codex | GPT-6 Astra |
|---|---|---|
| LMArena Vision | — | 1280 |
| Blueprint-Bench 2 | — | 49.7% |
| Furniture Assembly | — | 80% |
| LMArena Document | — | 1468 |

## Multilingual

- GPT-5.1-Codex: —
- GPT-6 Astra: 54.0 (#53)

| Benchmark | GPT-5.1-Codex | GPT-6 Astra |
|---|---|---|
| LMArena Non-English | — | 1431 |
| LMArena Chinese | — | 1495 |
| LMArena French | — | 1467 |
| LMArena Russian | — | 1434 |
| LMArena Spanish | — | 1412 |

## Instruction Following

- GPT-5.1-Codex: —
- GPT-6 Astra: 76.6 (#37)

| Benchmark | GPT-5.1-Codex | GPT-6 Astra |
|---|---|---|
| LMArena Instruction Following | — | 1454 |

## Long Context

- GPT-5.1-Codex: —
- GPT-6 Astra: 44.7 (#57)

| Benchmark | GPT-5.1-Codex | GPT-6 Astra |
|---|---|---|
| LMArena Longer Query | — | 1460 |

## Writing & Preference

- GPT-5.1-Codex: —
- GPT-6 Astra: 75.7 (#7)

| Benchmark | GPT-5.1-Codex | GPT-6 Astra |
|---|---|---|
| LMArena Text | — | 1443 |
| LMArena Creative Writing | — | 1423 |
| EQ-Bench Creative Writing | — | 2173 |
| LMArena Multi-Turn | — | 1457 |

## FAQ

### Is GPT-5.1-Codex better than GPT-6 Astra?

GPT-6 Astra is the stronger model overall, scoring 70.3 to 38.2 on the Noometry Index. GPT-5.1-Codex costs 5.8× less per token, which makes it the better buy when GPT-6 Astra's lead doesn't matter for your workload.

### Which is cheaper, GPT-5.1-Codex or GPT-6 Astra?

GPT-5.1-Codex is cheaper. It lists at $1.25 per million input tokens and $10 per million output tokens; GPT-6 Astra lists at $10 and $50.

### Is GPT-5.1-Codex or GPT-6 Astra better for coding?

GPT-6 Astra scores higher on coding benchmarks: 70.5 versus 41.7 in the Noometry coding category.

### Which has the bigger context window?

GPT-6 Astra does, with 1.05M tokens against 400K.

### How many benchmarks do GPT-5.1-Codex and GPT-6 Astra share?

3 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and GPT-6 Astra has 51.