GPT-5.6 Sol vs Claude Sonnet 5.5 vs Claude Opus 5
Claude Sonnet 5.5 comes out ahead, 72 to 66 and 66 on our weighted score, and it is the cheaper option too.
OpenAIGPT-5.6 Sol
66/100- ECI161.8
- Price$4.00 / $20.00
- Context1.05M
- Our pick
AnthropicClaude Sonnet 5.5
72/100- ECI165.2
- Price$2.00 / $10.00
- Context1M
- Anthropic
Claude Opus 5
66/100- ECI162.9
- Price$5.00 / $25.00
- Context1M
Claude Sonnet 5.5 is our pick
Claude Sonnet 5.5 is the better all-round choice, scoring 72/100 against GPT-5.6 Sol (66) and Claude Opus 5 (66). It leads on capability and price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityClaude Sonnet 5.5Capabilities Index (ECI): Claude Sonnet 5.5 165.2 · Claude Opus 5 162.9 · GPT-5.6 Sol 161.8
- Lowest priceClaude Sonnet 5.5Claude Sonnet 5.5 $4.00 · GPT-5.6 Sol $8.00 · Claude Opus 5 $10.00 per 1M tokens (3:1 blend)
- Longest contextGPT-5.6 SolGPT-5.6 Sol 1,050,000 · Claude Sonnet 5.5 1,000,000 · Claude Opus 5 1,000,000 tokens
- Widest inputsSame inputsGPT-5.6 Sol: Text, Images, PDFs · Claude Sonnet 5.5: Text, Images, PDFs · Claude Opus 5: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | GPT-5.6 Sol | Claude Sonnet 5.5 | Claude Opus 5 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 93 | 97 | 94 |
| Price | 25% | 7 | 21 | 2 |
| Inputs & features | 15% | 80 | 80 | 80 |
| Context window | 10% | 61 | 60 | 60 |
| Overall | 100% | 66/100 | 72/100 | 66/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-5.6 SolOpenAI | Claude Sonnet 5.5Anthropic | Claude Opus 5Anthropic |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 161.8 | 165.2 (best) | 162.9 |
| ECI rank | #8 of 148 | #3 of 148 (best) | #5 of 148 |
| GPQA DiamondGraduate-level science questions | 93.5% | 95.6% (best) | 93.9% |
| FrontierMath Tiers 1–3Research-level mathematics | 89.1% (best) | 88.8% | 85.6% |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% (best) | 100% (best) | 98.9% |
| SimpleQA VerifiedShort factual questions | 69.7% (best) | 46.5% | 59.9% |
| Price per million tokens | |||
| Input | $4.00 | $2.00 (best) | $5.00 |
| Output | $20.00 | $10.00 (best) | $25.00 |
| Cached input | $0.40 | $0.20 (best) | $0.50 |
| Blended (3:1) | $8.00 | $4.00 (best) | $10.00 |
| Long-context rate | Over 272K: $8.00 / $30.00 | Same rate | Same rate |
| Price source | Official OpenAI API | Official Anthropic API | Official Anthropic API |
| Limits | |||
| Context window | 1,050,000 tokens (best) | 1,000,000 tokens | 1,000,000 tokens |
| 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 | gpt-5.6-sol | claude-sonnet-5-5 | claude-opus-5 |
| API providers | 40 (best) | 23 | 35 |
| Released | Jul 9, 2026 | Sep 28, 2026 | Jul 24, 2026 |
| Knowledge cutoff | Feb 16, 2026 | Jun 2026 | May 2026 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- GPT-5.6 Sol$80.00
- Claude Sonnet 5.5$40.00
- Claude Opus 5$100.00
Which should you choose?
Which is better: GPT-5.6 Sol, Claude Sonnet 5.5 or Claude Opus 5?
Claude Sonnet 5.5 is the better all-round choice, scoring 72/100 against GPT-5.6 Sol (66) and Claude Opus 5 (66). It leads on capability and price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, GPT-5.6 Sol, Claude Sonnet 5.5 or Claude Opus 5?
Claude Sonnet 5.5 is cheaper at $2.00 input / $10.00 output per million tokens (official Anthropic API price). GPT-5.6 Sol costs $4.00 input / $20.00 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 $8.00 for GPT-5.6 Sol (2× as much) and $10.00 for Claude Opus 5 (2.5× as much).
Which scores higher on benchmarks?
Claude Sonnet 5.5 scores higher on the Capabilities Index (ECI): Claude Sonnet 5.5 165.2 (#3 of 148), Claude Opus 5 162.9 (#5 of 148) and GPT-5.6 Sol 161.8 (#8 of 148). The confidence ranges of the top two overlap (161.8–169.4 vs 160.2–166.7), so treat the gap as small. On individual benchmarks: GPQA Diamond — Claude Sonnet 5.5 95.6%, Claude Opus 5 93.9%, GPT-5.6 Sol 93.5%; FrontierMath Tiers 1–3 — GPT-5.6 Sol 89.1%, Claude Sonnet 5.5 88.8%, Claude Opus 5 85.6%; OTIS Mock AIME 2024–2025 — GPT-5.6 Sol 100%, Claude Sonnet 5.5 100%, Claude Opus 5 98.9%; SimpleQA Verified — GPT-5.6 Sol 69.7%, 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 GPT-5.6 Sol, Claude Sonnet 5.5 and Claude Opus 5 yet, so there is no like-for-like coding score. On overall capability, Claude Sonnet 5.5 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-5.6 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: GPT-5.6 Sol up to 128,000, Claude Sonnet 5.5 up to 128,000, Claude Opus 5 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GPT-5.6 Sol accepts text, images and PDFs; Claude Sonnet 5.5 accepts text, images and PDFs; Claude Opus 5 accepts text, images and PDFs. They handle the same number of input types.
Are any of these open source?
No. GPT-5.6 Sol, Claude Sonnet 5.5 and Claude Opus 5 are proprietary and only available through APIs and apps.
Which is newer?
Claude Sonnet 5.5 is the newest, released Sep 28, 2026. Claude Opus 5 came out Jul 24, 2026; GPT-5.6 Sol came out Jul 9, 2026. Knowledge cutoff: GPT-5.6 Sol Feb 16, 2026, Claude Sonnet 5.5 Jun 2026, Claude Opus 5 May 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.
