# GPT-5.5 vs GPT-6 Astra

As of October 21, 2026, GPT-6 Astra costs 100% more per input token than GPT-5.5 ($10.00 vs $5.00 per 1M) and has a 922K-token context window versus 1M.

- Page: https://models.litellm.ai/compare/gpt-5.5-vs-gpt-6-astra
- GPT-5.5: https://models.litellm.ai/models/gpt-5.5
- GPT-6 Astra: https://models.litellm.ai/models/gpt-6-astra

## Side by side

| | GPT-5.5 | GPT-6 Astra |
|---|---|---|
| Input, per 1M tokens | $5.00 | $10.00 |
| Output, per 1M tokens | $30.00 | $50.00 |
| Cache read, per 1M tokens | $0.50 | $1.00 |
| Cache write, per 1M tokens | – | $12.50 |
| Context window | 1,050,000 tokens | 922,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Image input | Yes | Yes |
| Tool calling | Yes | Yes |
| Structured output (JSON) | Yes | Yes |
| Prompt caching | Yes | Yes |
| Reasoning | Yes | Yes |
| Providers on LiteLLM | 10 | 8 |
| Price shown is from | OpenAI | OpenAI |
| Added to LiteLLM | April 2026 | September 3, 2026 |

Headline prices in USD per 1M tokens, from LiteLLM's model price file.

## Cheapest provider for each

- GPT-5.5: OpenAI at $5.00 input per 1M tokens (`gpt-5.5`)
- GPT-6 Astra: OpenAI at $10.00 input per 1M tokens (`gpt-6-astra`)

## Benchmark scores

| Benchmark | GPT-5.5 | GPT-6 Astra |
|---|---|---|
| Epoch Capabilities Index (Overall) | 159.7 | 168.8 |
| FrontierCode (Coding and agents) | 43.0% | 53.3% (max) |
| APEX-Agents (Coding and agents) | 55.1% | 64.7% |
| GPQA Diamond (Reasoning and knowledge) | 90.7% (low) | 95.8% (max) |
| ARC-AGI-2 (Reasoning and knowledge) | 85.0% (xhigh) | 95.0% (max) |
| SimpleQA Verified (Reasoning and knowledge) | 63.0% (xhigh) | 75.6% (max) |
| FrontierMath (tiers 1-3) (Math) | 85.3% (xhigh) | 93.7% (max) |
| FrontierMath (tier 4) (Math) | 72.5% (xhigh) | 97.6% (high) |
| OTIS Mock AIME 2024-2025 (Math) | 84.4% (low) | 100.0% (max) |

From the Epoch AI Benchmarking Hub (https://epoch.ai/benchmarks), CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/), data as of September 3, 2026: Epoch's own runs and results it collects from each benchmark's leaderboard. Higher is better.

## When to pick which

- GPT-5.5: Costs 50% less per input token: $5.00 vs $10.00 per 1M.
- GPT-5.5: Larger context window: 1,050,000 vs 922,000 tokens.

## FAQ

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

GPT-5.5 is cheaper at 3 input tokens per output token: $11.25 per 1M tokens blended ($5.00 input, $30.00 output), versus $20.00 ($10.00 and $50.00) for GPT-6 Astra, as of October 21, 2026.

### Which has the larger context window, GPT-5.5 or GPT-6 Astra?

GPT-5.5 has the larger context window: 1,050,000 tokens, versus 922,000 for GPT-6 Astra.

### Can I switch from GPT-5.5 to GPT-6 Astra without changing my code?

Yes. Through LiteLLM both use the OpenAI format, so switching means changing the model name from "gpt-5.5" to "gpt-6-astra", or pointing a LiteLLM gateway model alias at the other model. You can also use one as a fallback for the other.