GPT-5.5 Pro vs GPT-5.6 Sol
Too close to call on our weighted score (GPT-5.6 Sol 66, GPT-5.5 Pro 65). The right pick depends on what you value most.
OpenAIGPT-5.5 Pro
65/100- ECI162.4
- Price$30.00 / $180.00
- Context1.05M
- OpenAI
GPT-5.6 Sol
66/100- ECI161.8
- Price$4.00 / $20.00
- Context1.05M
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Make it a three-way comparison.
Too close to call
It is close. Our weighted score puts them within 1 points (GPT-5.6 Sol 66/100, GPT-5.5 Pro 65/100), so choose by what matters most for your work: GPT-5.5 Pro for raw capability and GPT-5.6 Sol on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGPT-5.5 ProCapabilities Index (ECI): GPT-5.5 Pro 162.4 · GPT-5.6 Sol 161.8
- Lowest priceGPT-5.6 SolGPT-5.6 Sol $8.00 · GPT-5.5 Pro $67.50 per 1M tokens (3:1 blend)
- Longest contextAbout the sameGPT-5.5 Pro 1,050,000 · GPT-5.6 Sol 1,050,000 tokens
- Widest inputsSame inputsGPT-5.5 Pro: Text, Images, PDFs · GPT-5.6 Sol: Text, Images, PDFs
- Self-hostingNo open weightsBoth are available only through APIs
| Measure | Weight | GPT-5.5 Pro | GPT-5.6 Sol |
|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 94 | 93 |
| Price | 25% | 0 | 7 |
| Inputs & features | 15% | 80 | 80 |
| Context window | 10% | 61 | 61 |
| Overall | 100% | 65/100 | 66/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-5.5 ProOpenAI | GPT-5.6 SolOpenAI |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | 162.4 (best) | 161.8 |
| ECI rank | #6 of 148 (best) | #8 of 148 |
| GPQA DiamondGraduate-level science questions | 93.9% (best) | 93.5% |
| FrontierMath Tiers 1–3Research-level mathematics | 87.7% | 89.1% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% | 100% |
| SimpleQA VerifiedShort factual questions | — | 69.7% |
| Price per million tokens | ||
| Input | $30.00 | $4.00 (best) |
| Output | $180.00 | $20.00 (best) |
| Cached input | — | $0.40 |
| Blended (3:1) | $67.50 | $8.00 (best) |
| Long-context rate | Over 272K: $60.00 / $270.00 | Over 272K: $8.00 / $30.00 |
| Price source | Official OpenAI API | Official OpenAI API |
| Limits | ||
| Context window | 1,050,000 tokens | 1,050,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | Yes | Yes |
| PDFs | Yes | Yes |
| Audio | No | No |
| Video | No | No |
| Reasoning | Yesmedium · high · xhigh | Yeslow · medium · high · xhigh · max |
| Tool calling | Yes | Yes |
| Structured output | Yes | Yes |
| Availability | ||
| Weights | Proprietary | Proprietary |
| API model ID | gpt-5.5-pro | gpt-5.6-sol |
| API providers | 19 | 40 (best) |
| Released | Apr 23, 2026 | Jul 9, 2026 |
| Knowledge cutoff | Dec 1, 2025 | 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.
- GPT-5.5 Pro$660.00
- GPT-5.6 Sol$80.00
Which should you choose?
Which is better: GPT-5.5 Pro or GPT-5.6 Sol?
It is close. Our weighted score puts them within 1 points (GPT-5.6 Sol 66/100, GPT-5.5 Pro 65/100), so choose by what matters most for your work: GPT-5.5 Pro for raw capability and GPT-5.6 Sol on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, GPT-5.5 Pro or GPT-5.6 Sol?
GPT-5.6 Sol is cheaper at $4.00 input / $20.00 output per million tokens (official OpenAI API price). GPT-5.5 Pro costs $30.00 input / $180.00 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 $67.50 for GPT-5.5 Pro (8.4× as much).
Which scores higher on benchmarks?
GPT-5.5 Pro scores higher on the Capabilities Index (ECI): GPT-5.5 Pro 162.4 (#6 of 148) and GPT-5.6 Sol 161.8 (#8 of 148). The confidence ranges of the top two overlap (159.0–166.0 vs 159.3–165.3), so treat the gap as small. On individual benchmarks: GPQA Diamond — GPT-5.5 Pro 93.9%, GPT-5.6 Sol 93.5%; FrontierMath Tiers 1–3 — GPT-5.6 Sol 89.1%, GPT-5.5 Pro 87.7%; OTIS Mock AIME 2024–2025 — GPT-5.5 Pro 100%, GPT-5.6 Sol 100%.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-5.5 Pro and GPT-5.6 Sol yet, so there is no like-for-like coding score. On overall capability, GPT-5.5 Pro leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.
Which has the bigger context window?
GPT-5.5 Pro and GPT-5.6 Sol share the same 1,050,000-token context window. Maximum output per response: GPT-5.5 Pro up to 128,000, GPT-5.6 Sol up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GPT-5.5 Pro 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. GPT-5.5 Pro and GPT-5.6 Sol are proprietary and only available through APIs and apps.
Which is newer?
GPT-5.6 Sol is the newest, released Jul 9, 2026. GPT-5.5 Pro came out Apr 23, 2026. Knowledge cutoff: GPT-5.5 Pro Dec 1, 2025, 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.
