Claude Sonnet 5.5 vs GPT-5.3 Codex vs GPT-6.1 Sol
Too close to call on our weighted score (GPT-6.1 Sol 47, Claude Sonnet 5.5 47, GPT-5.3 Codex 42). The right pick depends on what you value most.
AnthropicClaude Sonnet 5.5
47/100- ECI165.2
- Price$2.00 / $10.00
- Context1M
OpenAIGPT-5.3 Codex
42/100- ECI156.8
- Price$1.75 / $14.00
- Context400K
- OpenAI
GPT-6.1 Sol
47/100- ECI—
- Price$2.00 / $10.00
- Context1.05M
Too close to call
It is close. Our weighted score puts them within a point (GPT-6.1 Sol 47/100, Claude Sonnet 5.5 47/100, GPT-5.3 Codex 42/100), so choose by what matters most for your work: Claude Sonnet 5.5 on price and GPT-6.1 Sol for long inputs. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
- CapabilityNot enough dataNo independent benchmark covers every model here yet
- Lowest priceClaude Sonnet 5.5 and GPT-6.1 SolClaude Sonnet 5.5 $4.00 · GPT-6.1 Sol $4.00 · GPT-5.3 Codex $4.81 per 1M tokens (3:1 blend)
- Longest contextGPT-6.1 SolGPT-6.1 Sol 1,050,000 · Claude Sonnet 5.5 1,000,000 · GPT-5.3 Codex 400,000 tokens
- Widest inputsSame inputsClaude Sonnet 5.5: Text, Images, PDFs · GPT-5.3 Codex: 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 | GPT-5.3 Codex | GPT-6.1 Sol |
|---|---|---|---|---|
| Price | 50% | 21 | 18 | 21 |
| Inputs & features | 30% | 80 | 80 | 80 |
| Context window | 20% | 60 | 44 | 61 |
| Overall | 100% | 47/100 | 42/100 | 47/100 |
Left out because at least one model lacks the data: capability. The remaining weights were rescaled.
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Claude Sonnet 5.5Anthropic | GPT-5.3 CodexOpenAI | GPT-6.1 SolOpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 165.2 (best) | 156.8 | — |
| ECI rank | #3 of 148 (best) | #18 of 148 | — |
| GPQA DiamondGraduate-level science questions | 95.6% (best) | — | 95.4% |
| FrontierMath Tiers 1–3Research-level mathematics | 88.8% | — | 93.7% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% | — | 100% |
| SWE-bench VerifiedFixing real GitHub issues | — | 74.8% | — |
| SimpleQA VerifiedShort factual questions | 46.5% | — | 73.9% (best) |
| Price per million tokens | |||
| Input | $2.00 | $1.75 (best) | $2.00 |
| Output | $10.00 (best) | $14.00 | $10.00 (best) |
| Cached input | $0.20 | $0.175 | $0.10 (best) |
| Blended (3:1) | $4.00 (best) | $4.81 | $4.00 (best) |
| Long-context rate | Same rate | Same rate | Over 272K: $4.00 / $15.00 |
| Price source | Official Anthropic API | Official OpenAI API | Official OpenAI API |
| Limits | |||
| Context window | 1,000,000 tokens | 400,000 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 | 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 | gpt-5.3-codex | gpt-6.1-sol |
| API providers | 23 (best) | 19 | 21 |
| Released | Sep 28, 2026 | Feb 5, 2026 | Sep 29, 2026 |
| Knowledge cutoff | Jun 2026 | Aug 31, 2025 | 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
- GPT-5.3 Codex$45.50
- GPT-6.1 Sol$40.00
Which should you choose?
Which is better: Claude Sonnet 5.5, GPT-5.3 Codex or GPT-6.1 Sol?
It is close. Our weighted score puts them within a point (GPT-6.1 Sol 47/100, Claude Sonnet 5.5 47/100, GPT-5.3 Codex 42/100), so choose by what matters most for your work: Claude Sonnet 5.5 on price and GPT-6.1 Sol for long inputs. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
Which is cheaper, Claude Sonnet 5.5, GPT-5.3 Codex 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); GPT-5.3 Codex costs $1.75 input / $14.00 output per million tokens (official OpenAI 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 $4.81 for GPT-5.3 Codex (1.2× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers all three models yet. Claude Sonnet 5.5 has an ECI of 165.2, GPT-5.3 Codex has an ECI of 156.8 and GPT-6.1 Sol has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Sonnet 5.5 and GPT-6.1 Sol yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. 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 400,000 for GPT-5.3 Codex. Maximum output per response: Claude Sonnet 5.5 up to 128,000, GPT-5.3 Codex 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; GPT-5.3 Codex 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, GPT-5.3 Codex 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; GPT-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: Claude Sonnet 5.5 Jun 2026, GPT-5.3 Codex Aug 31, 2025, 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.
