High-volume, cost-sensitive work
Choose GPT-6 Astra
GPT-6 Astra costs 70% less on a typical mix of three input tokens for every output token ($20.00 against $67.50 per million tokens).
GPT-5.5 Pro vs GPT-6 Astra: price, context and capabilities
Choose GPT-6 Astra for high-volume, cost-sensitive work, writing and code generation, the latest release and the most recent knowledge; on the other points the two are level or the data is missing.
In short
- GPT-6 Astra is 70% cheaper than GPT-5.5 Pro at the headline price ($20.00 / 1M tokens vs $67.50 / 1M tokens).
- Both accept 1.05M tokens per request.
- GPT-6 Astra is the newer model (Sep 3, 2026, against Apr 24, 2026).
- Only GPT-6 Astra offers prompt caching.
Which should you choose?
Each answer below comes straight from the published prices, specifications and independent benchmark results.
Writing and code generation
Choose GPT-6 Astra
GPT-6 Astra charges $50.00 per million output tokens, against $180.00 for GPT-5.5 Pro. Output dominates the bill when answers are long.
Latest release
Choose GPT-6 Astra
GPT-6 Astra is the newer release (Sep 3, 2026, against Apr 24, 2026 for GPT-5.5 Pro).
Most recent knowledge
Choose GPT-6 Astra
GPT-6 Astra was trained on data up to April 2026, against December 2025 for GPT-5.5 Pro.
Monthly cost at three volumes
| Volume | GPT-5.5 Pro | GPT-6 Astra | Difference |
|---|---|---|---|
| Prototype: 1M input, 250K output tokens | $75.00 | $22.50 | GPT-6 Astra, $52.50 less |
| Production: 20M input, 5M output tokens | $1,500 | $450.00 | GPT-6 Astra, $1,050 less |
| Scale: 500M input, 100M output tokens | $33,000 | $10,000 | GPT-6 Astra, $23,000 less |
Standard rates, without caching or batch discounts. Volumes are per month.
Specifications side by side
| GPT-5.5 Pro | GPT-6 Astra | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Category | Language models | Language models |
| Status | Legacy | Generally available |
| Headline price | $67.50 / 1M tokens | $20.00 / 1M tokens |
| Input | $30.00 / 1M tokens | $10.00 / 1M tokens |
| Output | $180 / 1M tokens | $50.00 / 1M tokens |
| Cached input | No data | $1.00 / 1M tokens |
| Context window | 1.05M | 1.05M |
| Max output | 128k | 128k |
| Released | Apr 24, 2026 | Sep 3, 2026 |
| Knowledge cutoff | December 2025 | April 2026 |
| Licence | Proprietary | Proprietary |
| Capabilities | Vision, Reasoning, Tool calling, Structured output, Batch API | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API |
| API model id | gpt-5.5-pro | gpt-6-astra |
Benchmarks side by side
Leader in bold.
| Benchmark | GPT-5.5 Pro | GPT-6 Astra |
|---|---|---|
| Intelligence Index | No data | 52.7 |
| SciCode | No data | 56.5% |
| GPQA Diamond | No data | 96.1% |
| Humanity's Last Exam | No data | 54.7% |
| MMMU-Pro (visual reasoning) | No data | 86.9% |
| Long-context reasoning (AA-LCR) | No data | 80.7% |
Independent evaluations by Artificial Analysis, run the same way for every model, at the reasoning setting shown. Percentages unless marked as an index.
Frequently asked questions
Should I choose GPT-5.5 Pro or GPT-6 Astra?
Choose GPT-6 Astra for high-volume, cost-sensitive work, writing and code generation, the latest release and the most recent knowledge; on the other points the two are level or the data is missing.
Which is cheaper, GPT-5.5 Pro or GPT-6 Astra?
GPT-6 Astra is 70% cheaper than GPT-5.5 Pro at the headline price ($20.00 / 1M tokens vs $67.50 / 1M tokens).
Which has the larger context window, GPT-5.5 Pro or GPT-6 Astra?
Both accept 1.05M tokens per request.
What is the difference between GPT-5.5 Pro and GPT-6 Astra?
GPT-5.5 Pro is made by OpenAI and GPT-6 Astra by OpenAI. GPT-6 Astra is 70% cheaper than GPT-5.5 Pro at the headline price ($20.00 / 1M tokens vs $67.50 / 1M tokens). Both accept 1.05M tokens per request. GPT-6 Astra is the newer model (Sep 3, 2026, against Apr 24, 2026). Only GPT-6 Astra offers prompt caching.
How much do GPT-5.5 Pro and GPT-6 Astra cost per month?
At 20 million input and 5 million output tokens a month, GPT-5.5 Pro costs $1,500 and GPT-6 Astra costs $450.00, at standard rates.
Which is newer, GPT-5.5 Pro or GPT-6 Astra?
GPT-6 Astra was released on Sep 3, 2026 and GPT-5.5 Pro on Apr 24, 2026.