GPT-5.5 vs GPT-5.6 Sol vs Claude Opus 4.8
GPT-5.6 Sol comes out ahead, 66 to 63 and 63 on our weighted score, and it is the cheaper option too.
OpenAIGPT-5.5
63/100- ECI159.2
- Price$5.00 / $30.00
- Context1.05M
- Our pickOpenAI
GPT-5.6 Sol
66/100- ECI161.8
- Price$4.00 / $20.00
- Context1.05M
AnthropicClaude Opus 4.8
63/100- ECI158.3
- Price$5.00 / $25.00
- Context1M
GPT-5.6 Sol is our pick
GPT-5.6 Sol is the better all-round choice, scoring 66/100 against GPT-5.5 (63) and Claude Opus 4.8 (63). It leads on capability and price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGPT-5.6 SolCapabilities Index (ECI): GPT-5.6 Sol 161.8 · GPT-5.5 159.2 · Claude Opus 4.8 158.3
- Lowest priceGPT-5.6 SolGPT-5.6 Sol $8.00 · Claude Opus 4.8 $10.00 · GPT-5.5 $11.25 per 1M tokens (3:1 blend)
- Longest contextGPT-5.5 and GPT-5.6 SolGPT-5.5 1,050,000 · GPT-5.6 Sol 1,050,000 · Claude Opus 4.8 1,000,000 tokens
- Widest inputsSame inputsGPT-5.5: Text, Images, PDFs · GPT-5.6 Sol: Text, Images, PDFs · Claude Opus 4.8: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | GPT-5.5 | GPT-5.6 Sol | Claude Opus 4.8 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 90 | 93 | 89 |
| Price | 25% | 0 | 7 | 2 |
| Inputs & features | 15% | 80 | 80 | 80 |
| Context window | 10% | 61 | 61 | 60 |
| Overall | 100% | 63/100 | 66/100 | 63/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-5.5OpenAI | GPT-5.6 SolOpenAI | Claude Opus 4.8Anthropic |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 159.2 | 161.8 (best) | 158.3 |
| ECI rank | #10 of 148 | #8 of 148 (best) | #12 of 148 |
| GPQA DiamondGraduate-level science questions | 94.0% (best) | 93.5% | 91.0% |
| FrontierMath Tiers 1–3Research-level mathematics | 85.3% | 89.1% (best) | 80.0% |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% (best) | 100% (best) | 98.3% |
| SWE-bench VerifiedFixing real GitHub issues | 80.6% | — | — |
| SimpleQA VerifiedShort factual questions | 63.0% | 69.7% (best) | 53.0% |
| Price per million tokens | |||
| Input | $5.00 | $4.00 (best) | $5.00 |
| Output | $30.00 | $20.00 (best) | $25.00 |
| Cached input | $0.50 | $0.40 (best) | $0.50 |
| Blended (3:1) | $11.25 | $8.00 (best) | $10.00 |
| Long-context rate | Over 272K: $10.00 / $45.00 | Over 272K: $8.00 / $30.00 | Same rate |
| Price source | Official OpenAI API | Official OpenAI API | Official Anthropic API |
| Limits | |||
| Context window | 1,050,000 tokens (best) | 1,050,000 tokens (best) | 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 | 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-5.5 | gpt-5.6-sol | claude-opus-4-8 |
| API providers | 42 | 40 | 45 (best) |
| Released | Apr 23, 2026 | Jul 9, 2026 | May 28, 2026 |
| Knowledge cutoff | Dec 1, 2025 | Feb 16, 2026 | Jan 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-5.5$110.00
- GPT-5.6 Sol$80.00
- Claude Opus 4.8$100.00
Which should you choose?
Which is better: GPT-5.5, GPT-5.6 Sol or Claude Opus 4.8?
GPT-5.6 Sol is the better all-round choice, scoring 66/100 against GPT-5.5 (63) and Claude Opus 4.8 (63). It leads on capability and price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, GPT-5.5, GPT-5.6 Sol or Claude Opus 4.8?
GPT-5.6 Sol is cheaper at $4.00 input / $20.00 output per million tokens (official OpenAI API price). Claude Opus 4.8 costs $5.00 input / $25.00 output per million tokens (official Anthropic API price); GPT-5.5 costs $5.00 input / $30.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $8.00 per million tokens for GPT-5.6 Sol versus $10.00 for Claude Opus 4.8 (1.3× as much) and $11.25 for GPT-5.5 (1.4× as much).
Which scores higher on benchmarks?
GPT-5.6 Sol scores higher on the Capabilities Index (ECI): GPT-5.6 Sol 161.8 (#8 of 148), GPT-5.5 159.2 (#10 of 148) and Claude Opus 4.8 158.3 (#12 of 148). The confidence ranges of the top two overlap (159.3–165.3 vs 156.9–162.4), so treat the gap as small. On individual benchmarks: GPQA Diamond — GPT-5.5 94.0%, GPT-5.6 Sol 93.5%, Claude Opus 4.8 91.0%; FrontierMath Tiers 1–3 — GPT-5.6 Sol 89.1%, GPT-5.5 85.3%, Claude Opus 4.8 80.0%; OTIS Mock AIME 2024–2025 — GPT-5.5 100%, GPT-5.6 Sol 100%, Claude Opus 4.8 98.3%; SimpleQA Verified — GPT-5.6 Sol 69.7%, GPT-5.5 63.0%, Claude Opus 4.8 53.0%.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-5.6 Sol and Claude Opus 4.8 yet, so there is no like-for-like coding score. On overall capability, GPT-5.6 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-5.5 and GPT-5.6 Sol have the largest context windows (1,050,000 and 1,050,000 tokens), against 1,000,000 for Claude Opus 4.8. Maximum output per response: GPT-5.5 up to 128,000, GPT-5.6 Sol up to 128,000, Claude Opus 4.8 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GPT-5.5 accepts text, images and PDFs; GPT-5.6 Sol accepts text, images and PDFs; Claude Opus 4.8 accepts text, images and PDFs. They handle the same number of input types.
Are any of these open source?
No. GPT-5.5, GPT-5.6 Sol and Claude Opus 4.8 are proprietary and only available through APIs and apps.
Which is newer?
GPT-5.6 Sol is the newest, released Jul 9, 2026. Claude Opus 4.8 came out May 28, 2026; GPT-5.5 came out Apr 23, 2026. Knowledge cutoff: GPT-5.5 Dec 1, 2025, GPT-5.6 Sol Feb 16, 2026, Claude Opus 4.8 Jan 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.
