High-volume, cost-sensitive work
Choose GPT-5.1
GPT-5.1 costs 14% less on a typical mix of three input tokens for every output token ($3.44 against $4.00 per million tokens).
Claude Sonnet 5.5 vs GPT-5.1: price, context and capabilities
Choose Claude Sonnet 5.5 for reused prompts and documents (RAG, agents), very long inputs, reasoning over long documents, the latest release and the most recent knowledge. Choose GPT-5.1 for high-volume, cost-sensitive work.
In short
- GPT-5.1 is 14% cheaper than Claude Sonnet 5.5 at the headline price ($3.44 / 1M tokens vs $4.00 / 1M tokens).
- Claude Sonnet 5.5 reads more per request: 1M tokens against 400k.
- Claude Sonnet 5.5 is the newer model (September 2026, against Nov 13, 2025).
Which should you choose?
Each answer below comes straight from the published prices, specifications and independent benchmark results.
Reused prompts and documents (RAG, agents)
Choose Claude Sonnet 5.5
Claude Sonnet 5.5 charges $0.10 per million cached input tokens, against $0.13 for GPT-5.1.
Very long inputs
Choose Claude Sonnet 5.5
Claude Sonnet 5.5 reads up to 1M tokens per request, against 400k for GPT-5.1.
Reasoning over long documents
Choose Claude Sonnet 5.5
Claude Sonnet 5.5 scores 82.7% on Long-context reasoning (AA-LCR), against 80% for GPT-5.1.
Latest release
Choose Claude Sonnet 5.5
Claude Sonnet 5.5 is the newer release (September 2026, against Nov 13, 2025 for GPT-5.1).
Most recent knowledge
Choose Claude Sonnet 5.5
Claude Sonnet 5.5 was trained on data up to June 2026, against September 2024 for GPT-5.1.
Monthly cost at three volumes
| Volume | Claude Sonnet 5.5 | GPT-5.1 | Difference |
|---|---|---|---|
| Prototype: 1M input, 250K output tokens | $4.50 | $3.75 | GPT-5.1, $0.75 less |
| Production: 20M input, 5M output tokens | $90.00 | $75.00 | GPT-5.1, $15.00 less |
| Scale: 500M input, 100M output tokens | $2,000 | $1,625 | GPT-5.1, $375.00 less |
Standard rates, without caching or batch discounts. Volumes are per month.
Specifications side by side
| Claude Sonnet 5.5 | GPT-5.1 | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Category | Language models | Language models |
| Status | Generally available | Deprecated |
| Headline price | $4.00 / 1M tokens | $3.44 / 1M tokens |
| Input | $2.00 / 1M tokens | $1.25 / 1M tokens |
| Output | $10.00 / 1M tokens | $10.00 / 1M tokens |
| Cached input | $0.10 / 1M tokens | $0.125 / 1M tokens |
| Context window | 1M | 400k |
| Max output | 128k | 128k |
| Released | September 2026 | Nov 13, 2025 |
| Knowledge cutoff | June 2026 | September 2024 |
| Licence | Proprietary | Proprietary |
| Capabilities | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API |
| API model id | claude-sonnet-5-5 | gpt-5.1 |
Benchmarks side by side
Leader in bold.
| Benchmark | Claude Sonnet 5.5 | GPT-5.1 |
|---|---|---|
| Humanity's Last Exam | 55% | 28.5% |
| Long-context reasoning (AA-LCR) | 82.7% | 80% |
| Intelligence Index | 56 | No data |
| SciCode | 61% | No data |
| Terminal-Bench Hard | No data | 45.5% |
| GPQA Diamond | No data | 87.3% |
| IFBench (instruction following) | No data | 72.9% |
| τ²-Bench (agentic tool use) | No data | 81.9% |
| MMMU-Pro (visual reasoning) | No data | 75.5% |
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 Claude Sonnet 5.5 or GPT-5.1?
Choose Claude Sonnet 5.5 for reused prompts and documents (RAG, agents), very long inputs, reasoning over long documents, the latest release and the most recent knowledge. Choose GPT-5.1 for high-volume, cost-sensitive work.
Which is cheaper, Claude Sonnet 5.5 or GPT-5.1?
GPT-5.1 is 14% cheaper than Claude Sonnet 5.5 at the headline price ($3.44 / 1M tokens vs $4.00 / 1M tokens).
Which has the larger context window, Claude Sonnet 5.5 or GPT-5.1?
Claude Sonnet 5.5 reads more per request: 1M tokens against 400k.
What is the difference between Claude Sonnet 5.5 and GPT-5.1?
Claude Sonnet 5.5 is made by Anthropic and GPT-5.1 by OpenAI. GPT-5.1 is 14% cheaper than Claude Sonnet 5.5 at the headline price ($3.44 / 1M tokens vs $4.00 / 1M tokens). Claude Sonnet 5.5 reads more per request: 1M tokens against 400k. Claude Sonnet 5.5 is the newer model (September 2026, against Nov 13, 2025).
How much do Claude Sonnet 5.5 and GPT-5.1 cost per month?
At 20 million input and 5 million output tokens a month, Claude Sonnet 5.5 costs $90.00 and GPT-5.1 costs $75.00, at standard rates.
Which is newer, Claude Sonnet 5.5 or GPT-5.1?
Claude Sonnet 5.5 was released on September 2026 and GPT-5.1 on Nov 13, 2025.