Claude Sonnet 5.5 vs Claude Opus 5 vs GPT-6.1 Sol
GPT-6.1 Sol comes out ahead, 69 to 65 and 61 on our weighted score.
AnthropicClaude Sonnet 5.5
65/100- ECI165.2
- Price$2.00 / $10.00
- Context1M
- Anthropic
Claude Opus 5
61/100- ECI162.9
- Price$5.00 / $25.00
- Context1M
- Our pick
OpenAIGPT-6.1 Sol
69/100- ECI—
- Price$2.00 / $10.00
- Context1.05M
GPT-6.1 Sol is our pick
GPT-6.1 Sol is the better all-round choice, scoring 69/100 against Claude Sonnet 5.5 (65) and Claude Opus 5 (61). It leads on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%. Capability uses the average of shared benchmarks (GPQA Diamond, FrontierMath Tiers 1–3, OTIS Mock AIME 2024–2025 and SimpleQA Verified), because GPT-6.1 Sol has no Capabilities Index score yet.
- CapabilityGPT-6.1 SolShared benchmarks: GPT-6.1 Sol 90.7% · Claude Opus 5 84.6% · Claude Sonnet 5.5 82.7%
- Lowest priceClaude Sonnet 5.5 and GPT-6.1 SolClaude Sonnet 5.5 $4.00 · GPT-6.1 Sol $4.00 · Claude Opus 5 $10.00 per 1M tokens (3:1 blend)
- Longest contextGPT-6.1 SolGPT-6.1 Sol 1,050,000 · Claude Sonnet 5.5 1,000,000 · Claude Opus 5 1,000,000 tokens
- Widest inputsSame inputsClaude Sonnet 5.5: Text, Images, PDFs · Claude Opus 5: Text, Images, PDFs · GPT-6.1 Sol: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Claude Sonnet 5.5 | Claude Opus 5 | GPT-6.1 Sol |
|---|---|---|---|---|
| CapabilityShared benchmarks | 50% | 83 | 85 | 91 |
| Price | 25% | 21 | 2 | 21 |
| Inputs & features | 15% | 80 | 80 | 80 |
| Context window | 10% | 60 | 60 | 61 |
| Overall | 100% | 65/100 | 61/100 | 69/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Claude Sonnet 5.5Anthropic | Claude Opus 5Anthropic | GPT-6.1 SolOpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 165.2 (best) | 162.9 | — |
| ECI rank | #3 of 148 (best) | #5 of 148 | — |
| GPQA DiamondGraduate-level science questions | 95.6% (best) | 93.9% | 95.4% |
| FrontierMath Tiers 1–3Research-level mathematics | 88.8% | 85.6% | 93.7% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% (best) | 98.9% | 100% (best) |
| SimpleQA VerifiedShort factual questions | 46.5% | 59.9% | 73.9% (best) |
| Price per million tokens | |||
| Input | $2.00 (best) | $5.00 | $2.00 (best) |
| Output | $10.00 (best) | $25.00 | $10.00 (best) |
| Cached input | $0.20 | $0.50 | $0.10 (best) |
| Blended (3:1) | $4.00 (best) | $10.00 | $4.00 (best) |
| Long-context rate | Same rate | Same rate | Over 272K: $4.00 / $15.00 |
| Price source | Official Anthropic API | Official Anthropic API | Official OpenAI API |
| Limits | |||
| Context window | 1,000,000 tokens | 1,000,000 tokens | 1,050,000 tokens (best) |
| Max output | 128,000 tokens | 128,000 tokens | 128,000 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | No | No | No |
| Video | No | No | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh · max | Yeslow · medium · high · xhigh · max |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | claude-sonnet-5-5 | claude-opus-5 | gpt-6.1-sol |
| API providers | 23 | 35 (best) | 21 |
| Released | Sep 28, 2026 | Jul 24, 2026 | Sep 29, 2026 |
| Knowledge cutoff | Jun 2026 | May 2026 | Apr 30, 2026 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Claude Sonnet 5.5$40.00
- Claude Opus 5$100.00
- GPT-6.1 Sol$40.00
Which should you choose?
Which is better: Claude Sonnet 5.5, Claude Opus 5 or GPT-6.1 Sol?
GPT-6.1 Sol is the better all-round choice, scoring 69/100 against Claude Sonnet 5.5 (65) and Claude Opus 5 (61). It leads on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%. Capability uses the average of shared benchmarks (GPQA Diamond, FrontierMath Tiers 1–3, OTIS Mock AIME 2024–2025 and SimpleQA Verified), because GPT-6.1 Sol has no Capabilities Index score yet.
Which is cheaper, Claude Sonnet 5.5, Claude Opus 5 or GPT-6.1 Sol?
Claude Sonnet 5.5 is cheaper at $2.00 input / $10.00 output per million tokens (official Anthropic API price). GPT-6.1 Sol costs $2.00 input / $10.00 output per million tokens (official OpenAI API price); Claude Opus 5 costs $5.00 input / $25.00 output per million tokens (official Anthropic API price). At a typical mix of three input tokens to one output token, that is $4.00 per million tokens for Claude Sonnet 5.5 versus $4.00 for GPT-6.1 Sol (1× as much) and $10.00 for Claude Opus 5 (2.5× as much).
Which scores higher on benchmarks?
Not every model here has a Capabilities Index score, so we compare the average of shared benchmarks (GPQA Diamond, FrontierMath Tiers 1–3, OTIS Mock AIME 2024–2025 and SimpleQA Verified): GPT-6.1 Sol 90.7%, Claude Opus 5 84.6% and Claude Sonnet 5.5 82.7%. On individual benchmarks: GPQA Diamond — Claude Sonnet 5.5 95.6%, GPT-6.1 Sol 95.4%, Claude Opus 5 93.9%; FrontierMath Tiers 1–3 — GPT-6.1 Sol 93.7%, Claude Sonnet 5.5 88.8%, Claude Opus 5 85.6%; OTIS Mock AIME 2024–2025 — Claude Sonnet 5.5 100%, GPT-6.1 Sol 100%, Claude Opus 5 98.9%; SimpleQA Verified — GPT-6.1 Sol 73.9%, Claude Opus 5 59.9%, Claude Sonnet 5.5 46.5%.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Sonnet 5.5, Claude Opus 5 and GPT-6.1 Sol yet, so there is no like-for-like coding score. On overall capability, GPT-6.1 Sol leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.
Which has the bigger context window?
GPT-6.1 Sol has the largest context window at 1,050,000 tokens, against 1,000,000 for Claude Sonnet 5.5 and 1,000,000 for Claude Opus 5. Maximum output per response: Claude Sonnet 5.5 up to 128,000, Claude Opus 5 up to 128,000, GPT-6.1 Sol up to 128,000 tokens.
Which can read images, PDFs, audio or video?
Claude Sonnet 5.5 accepts text, images and PDFs; Claude Opus 5 accepts text, images and PDFs; GPT-6.1 Sol accepts text, images and PDFs. They handle the same number of input types.
Are any of these open source?
No. Claude Sonnet 5.5, Claude Opus 5 and GPT-6.1 Sol are proprietary and only available through APIs and apps.
Which is newer?
GPT-6.1 Sol is the newest, released Sep 29, 2026. Claude Sonnet 5.5 came out Sep 28, 2026; Claude Opus 5 came out Jul 24, 2026. Knowledge cutoff: Claude Sonnet 5.5 Jun 2026, Claude Opus 5 May 2026, GPT-6.1 Sol Apr 30, 2026.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
