# GPT-5.5 Pro vs GPT-6 Astra

> GPT-6 Astra is the stronger model overall, scoring 70.8 to 64.3 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-5-pro-vs-gpt-6-astra
- Last updated: 2026-10-10
- Shared benchmarks: 11

## Summary

- They share 11 benchmarks with published results for both. GPT-5.5 Pro scores higher in 0 categories and GPT-6 Astra in 3 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-6 Astra leads 85.1 to 73.3.
- The biggest single-benchmark swing is FrontierMath Tier 4: 78% for GPT-5.5 Pro and 97.6% for GPT-6 Astra.
- GPT-6 Astra is cheaper at $10 / $50 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.

## Snapshot

| | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 64.3 | 70.8 |
| Rank | 8 | 1 |
| Context | 1.05M | 1.05M |
| Input $/M | $30 | $10 |
| Output $/M | $180 | $50 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.5 Pro: —
- GPT-6 Astra: 73.7 (#2)

| Benchmark | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| DeepSWE | — | 74.1% |
| FrontierCode | — | 53.3% |
| LMArena WebDev | — | 1786 |
| FrontierSWE | — | 65.5% |
| SciCode | — | 56.5% |
| GSO | — | 79.4% |
| WeirdML | — | 93.6% |
| LMArena Coding | — | 1487 |
| MirrorCode | — | 46.7% |
| ALE-Bench | — | 2,951 |

## Agentic & Tool Use

- GPT-5.5 Pro: —
- GPT-6 Astra: 52.9 (#3)

| Benchmark | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| APEX-Agents | — | 64.7% |
| Remote Labor Index | — | 20.8% |
| BALROG | — | 68.3% |
| GDP.pdf | — | 34.2% |
| Vending-Bench 2 | — | 15,515 |

## Reasoning

- GPT-5.5 Pro: 73.3 (#10)
- GPT-6 Astra: 85.1 (#1)

| Benchmark | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| ARC-AGI-2 | 84.6% | 95% |
| ARC-AGI-1 | 96.5% | 98.5% |
| CritPt | 30.6% | 31.7% |
| Chess Puzzles | 64% | 72% |
| DTBench | 96% | 97.3% |
| LMCA | 53.9% | 64.4% |
| Epoch Capabilities Index | 162.07 | 166.45 |
| SimpleBench | 76.9% | — |
| NYT Connections (extended) | — | 98.1% |
| EBR-Bench | — | 76.2% |
| LMArena Hard Prompts | — | 1462 |
| Mystery Game Puzzles | — | 84% |
| Bench to the Future 3 | — | 0.14 |

## Math

- GPT-5.5 Pro: 84.0 (#10)
- GPT-6 Astra: 93.5 (#2)

| Benchmark | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| FrontierMath (Tiers 1-3) | 87.7% | 93.7% |
| FrontierMath Tier 4 | 78% | 97.6% |
| OTIS Mock AIME 2024-2025 | 100% | 100% |
| ProofBench | — | 99% |
| LMArena Math | — | 1465 |
| FrontierMath (Feb 2025 set) | 52.4% | — |
| FrontierMath Erdős | — | 2.9% |
| FrontierMath Tier 4 (v1) | 39.6% | — |

## Knowledge

- GPT-5.5 Pro: 64.1 (#19)
- GPT-6 Astra: 75.3 (#1)

| Benchmark | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| GPQA Diamond | 93.9% | 95.8% |
| Humanity's Last Exam | — | 54.8% |
| SimpleQA Verified | — | 75.6% |
| Vectara Hallucination Rate | — | 8.7% |
| LMArena Expert | — | 1483 |

## Multimodal

- GPT-5.5 Pro: —
- GPT-6 Astra: 55.0 (#3)

| Benchmark | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| LMArena Vision | — | 1281 |
| Blueprint-Bench 2 | — | 49.7% |
| Furniture Assembly | — | 80% |
| LMArena Document | — | 1468 |

## Multilingual

- GPT-5.5 Pro: —
- GPT-6 Astra: 53.7 (#61)

| Benchmark | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| LMArena Non-English | — | 1430 |
| LMArena Chinese | — | 1484 |
| LMArena French | — | 1456 |
| LMArena German | — | 1440 |
| LMArena Japanese | — | 1379 |
| LMArena Korean | — | 1426 |
| LMArena Russian | — | 1436 |
| LMArena Spanish | — | 1407 |

## Instruction Following

- GPT-5.5 Pro: —
- GPT-6 Astra: 76.3 (#44)

| Benchmark | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| LMArena Instruction Following | — | 1450 |

## Long Context

- GPT-5.5 Pro: —
- GPT-6 Astra: 44.5 (#62)

| Benchmark | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| LMArena Longer Query | — | 1456 |

## Writing & Preference

- GPT-5.5 Pro: —
- GPT-6 Astra: 75.3 (#7)

| Benchmark | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| LMArena Text | — | 1441 |
| LMArena Creative Writing | — | 1418 |
| EQ-Bench Creative Writing | — | 2173 |
| LMArena Multi-Turn | — | 1448 |

## FAQ

### Is GPT-5.5 Pro better than GPT-6 Astra?

GPT-6 Astra is the stronger model overall, scoring 70.8 to 64.3 on the Noometry Index.

### Which is cheaper, GPT-5.5 Pro or GPT-6 Astra?

GPT-6 Astra is cheaper. It lists at $10 per million input tokens and $50 per million output tokens; GPT-5.5 Pro lists at $30 and $180.

### Which has the bigger context window?

Both accept 1.05M tokens.

### How many benchmarks do GPT-5.5 Pro and GPT-6 Astra share?

11 benchmarks have published results for both models. GPT-5.5 Pro has 14 scored results on Noometry and GPT-6 Astra has 56.