GPT-5.1 Reasoning: pricing, context window and benchmarks
GPT-5.1 Reasoning is a frontier model from OpenAI. It offers a 400,000-token context window, costs $20.27 per million input tokens and $82.11 per million output tokens, and averages 88.3 across the index's benchmark suite.
Pricing
GPT-5.1 Reasoning costs $20.27 per million input tokens and $82.11 per million output tokens. A blended 3:1 input-to-output mix works out to about $35.73 per million tokens. Cached input is listed at $2.09 per million tokens.
| Item | Price | Notes |
|---|---|---|
| Input | $20.27 | per 1M tokens |
| Output | $82.11 | per 1M tokens |
| Cached input | $2.09 | per 1M tokens |
| Blended 3:1 | $35.73 | estimate per 1M tokens |
| 1M in + 1M out | $102.38 | estimate |
Benchmarks
Scores below are modelled estimates on a 0–100 scale. Use them to compare relative position, not as official vendor results.
| Benchmark | Score | Rank | Percentile | Relative |
|---|---|---|---|---|
| MMLU-Pro | 90.0 | 6 | 99th | |
| GPQA Diamond | 85.6 | 4 | 99th | |
| SWE-bench Verified | 76.0 | 30 | 95th | |
| HumanEval | 92.9 | 10 | 98th | |
| MATH-500 | 95.9 | 2 | 100th | |
| AIME 2025 | 85.0 | 39 | 94th | |
| LiveCodeBench | 80.9 | 33 | 95th | |
| IFEval | 94.6 | 8 | 99th | |
| TruthfulQA | 90.0 | 3 | 100th | |
| HellaSwag | 94.4 | 9 | 99th | |
| MMMU | 86.2 | 2 | 100th | |
| Arena Elo | 1485.9 | 14 | 98th |
What GPT-5.1 Reasoning is good for
GPT-5.1 Reasoning sits in the frontier tier of the index. It is aimed at work where answer quality matters more than unit cost: hard reasoning, multi-step coding, document analysis and multimodal inputs. At $20.27 per million input tokens and a 400,000-token context window, it is a premium option, so reserve it for tasks where a cheaper model measurably fails.
Strengths
- Top-tier average benchmark score (88.3), placing it #4 of 600.
- Large 400,000-token context window for long documents and agent traces.
- Accepts more than text, including image input where the provider supports it.
- Reasoning-oriented profile, useful for multi-step problems and structured analysis.
- Coding benchmarks are a relative strength within its tier.
Trade-offs
- Proprietary licence: you cannot download the weights or self-host the model.
- Premium input pricing at $20.27 per million tokens.
- Cost can climb quickly on long outputs and high-volume traffic.
How it compares
| Model | Provider | Context | Input / 1M | Avg score |
|---|---|---|---|---|
| GPT-5.1 Reasoning | OpenAI | 400000 | $20.27 | 88.3 |
| Claude Opus 4.5 Reasoning | Anthropic | 2000000 | $20.91 | 88.2 |
| GPT-5.2 | OpenAI | 2000000 | $19.71 | 88.0 |
| GPT-5.1 Max | OpenAI | 2000000 | $20.50 | 87.9 |
| Gemini 3 Pro Max | Google DeepMind | 2000000 | $20.57 | 87.9 |
| GPT-5.1 Pro | OpenAI | 200000 | $19.77 | 87.8 |
FAQ
How much does GPT-5.1 Reasoning cost?
GPT-5.1 Reasoning is listed at $20.27 per million input tokens and $82.11 per million output tokens. Cached input is $2.09 per million tokens. A blended 3:1 input-to-output mix is about $35.73 per million tokens.
What is the context window of GPT-5.1 Reasoning?
GPT-5.1 Reasoning has a context window of 400,000 tokens and can emit up to 128,000 output tokens per request in this index.
Is GPT-5.1 Reasoning open weights?
No. GPT-5.1 Reasoning is a proprietary model with a proprietary licence, so you cannot download the weights.
How does GPT-5.1 Reasoning score on benchmarks?
GPT-5.1 Reasoning averages 88.3 across the scored benchmarks in this index, ranking #4 of 600 models. Its strongest relative result is MMMU at 86.2.
What is GPT-5.1 Reasoning best for?
GPT-5.1 Reasoning sits in the frontier tier of the index. It is aimed at work where answer quality matters more than unit cost: hard reasoning, multi-step coding, document analysis and multimodal inputs. At $20.27 per million input tokens and a 400,000-token context window, it is a premium option, so reserve it for tasks where a cheaper model measurably fails.