Claude Opus 5 vs Claude Sonnet 5.5 vs GPT-5.6 Sol
Claude Sonnet 5.5 comes out ahead, 72 to 66 and 66 on our weighted score, and it is the cheaper option too.
AnthropicClaude Opus 5
66/100- ECI162.9
- Price$5.00 / $25.00
- Context1M
- Our pickAnthropic
Claude Sonnet 5.5
72/100- ECI165.2
- Price$2.00 / $10.00
- Context1M
OpenAIGPT-5.6 Sol
66/100- ECI161.8
- Price$4.00 / $20.00
- Context1.05M
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 Opus 5 1,000,000 · Claude Sonnet 5.5 1,000,000 tokens
- Widest inputsSame inputsClaude Opus 5: Text, Images, PDFs · Claude Sonnet 5.5: Text, Images, PDFs · GPT-5.6 Sol: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Claude Opus 5 | Claude Sonnet 5.5 | GPT-5.6 Sol |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 94 | 97 | 93 |
| Price | 25% | 2 | 21 | 7 |
| Inputs & features | 15% | 80 | 80 | 80 |
| Context window | 10% | 60 | 60 | 61 |
| 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 | Claude Opus 5Anthropic | Claude Sonnet 5.5Anthropic | GPT-5.6 SolOpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 162.9 | 165.2 (best) | 161.8 |
| ECI rank | #5 of 148 | #3 of 148 (best) | #8 of 148 |
| GPQA DiamondGraduate-level science questions | 93.9% | 95.6% (best) | 93.5% |
| FrontierMath Tiers 1–3Research-level mathematics | 85.6% | 88.8% | 89.1% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | 98.9% | 100% (best) | 100% (best) |
| SimpleQA VerifiedShort factual questions | 59.9% | 46.5% | 69.7% (best) |
| Price per million tokens | |||
| Input | $5.00 | $2.00 (best) | $4.00 |
| Output | $25.00 | $10.00 (best) | $20.00 |
| Cached input | $0.50 | $0.20 (best) | $0.40 |
| Blended (3:1) | $10.00 | $4.00 (best) | $8.00 |
| Long-context rate | Same rate | Same rate | Over 272K: $8.00 / $30.00 |
| 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-opus-5 | claude-sonnet-5-5 | gpt-5.6-sol |
| API providers | 35 | 23 | 40 (best) |
| Released | Jul 24, 2026 | Sep 28, 2026 | Jul 9, 2026 |
| Knowledge cutoff | May 2026 | Jun 2026 | Feb 16, 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 Opus 5$100.00
- Claude Sonnet 5.5$40.00
- GPT-5.6 Sol$80.00
Which should you choose?
Which is better: Claude Opus 5, Claude Sonnet 5.5 or GPT-5.6 Sol?
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, Claude Opus 5, Claude Sonnet 5.5 or GPT-5.6 Sol?
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 — Claude Sonnet 5.5 100%, GPT-5.6 Sol 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 Claude Opus 5, Claude Sonnet 5.5 and GPT-5.6 Sol 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 Opus 5 and 1,000,000 for Claude Sonnet 5.5. Maximum output per response: Claude Opus 5 up to 128,000, Claude Sonnet 5.5 up to 128,000, GPT-5.6 Sol up to 128,000 tokens.
Which can read images, PDFs, audio or video?
Claude Opus 5 accepts text, images and PDFs; Claude Sonnet 5.5 accepts text, images and PDFs; GPT-5.6 Sol accepts text, images and PDFs. They handle the same number of input types.
Are any of these open source?
No. Claude Opus 5, Claude Sonnet 5.5 and GPT-5.6 Sol 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: Claude Opus 5 May 2026, Claude Sonnet 5.5 Jun 2026, GPT-5.6 Sol Feb 16, 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.
