GPT-5 Chat vs Claude Sonnet 5.5
Claude Sonnet 5.5 comes out ahead, 46 to 31 on our weighted score, though GPT-5 Chat is 14% cheaper per token.
OpenAIGPT-5 Chat
31/100- ECI—
- Price$1.25 / $10.00
- Context400K
- Our pick
AnthropicClaude Sonnet 5.5
46/100- ECI166.7
- Price$2.00 / $10.00
- Context1M
Add a model
Make it a three-way comparison.
Claude Sonnet 5.5 is our pick
Claude Sonnet 5.5 is the better all-round choice, scoring 46/100 against GPT-5 Chat (31). It leads on inputs & features and context window. GPT-5 Chat wins on price. 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 priceGPT-5 ChatGPT-5 Chat $3.44 · Claude Sonnet 5.5 $4.00 per 1M tokens (3:1 blend)
- Longest contextClaude Sonnet 5.5Claude Sonnet 5.5 1,000,000 · GPT-5 Chat 400,000 tokens
- Widest inputsClaude Sonnet 5.5GPT-5 Chat: Text, Images · Claude Sonnet 5.5: Text, Images, PDFs
- Self-hostingNo open weightsBoth are available only through APIs
| Measure | Weight | GPT-5 Chat | Claude Sonnet 5.5 |
|---|---|---|---|
| Price | 50% | 23 | 20 |
| Inputs & features | 30% | 35 | 80 |
| Context window | 20% | 44 | 60 |
| Overall | 100% | 31/100 | 46/100 |
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 | GPT-5 ChatOpenAI | Claude Sonnet 5.5Anthropic |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | — | 166.7 |
| ECI rank | — | #5 of 165 |
| GPQA DiamondGraduate-level science questions | — | 95.6% |
| FrontierMath Tiers 1–3Research-level mathematics | — | 88.8% |
| OTIS Mock AIME 2024–2025Competition mathematics | — | 100% |
| SimpleQA VerifiedShort factual questions | — | 46.5% |
| Price per million tokens | ||
| Input | $1.25 (best) | $2.00 |
| Output | $10.00 | $10.00 |
| Cached input | — | $0.10 |
| Blended (3:1) | $3.44 (best) | $4.00 |
| Long-context rate | Same rate | Same rate |
| Price source | Median of 5 providers | Official Anthropic API |
| Limits | ||
| Context window | 400,000 tokens | 1,000,000 tokens (best) |
| Max output | 128,000 tokens | 128,000 tokens |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | Yes | Yes |
| PDFs | No | Yes |
| Audio | No | No |
| Video | No | No |
| Reasoning | Yes | Yeslow · medium · high · xhigh · max |
| Tool calling | No | Yes |
| Structured output | No | Yes |
| Availability | ||
| Weights | Proprietary | Proprietary |
| API model ID | — | claude-sonnet-5-5 |
| API providers | 5 | 34 (best) |
| Released | Aug 7, 2025 | Sep 28, 2026 |
| Knowledge cutoff | Sep 30, 2024 | Jun 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 Chat$32.50
- Claude Sonnet 5.5$40.00
Which should you choose?
Which is better: GPT-5 Chat or Claude Sonnet 5.5?
Claude Sonnet 5.5 is the better all-round choice, scoring 46/100 against GPT-5 Chat (31). It leads on inputs & features and context window. GPT-5 Chat wins on price. 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, GPT-5 Chat or Claude Sonnet 5.5?
GPT-5 Chat is cheaper at $1.25 input / $10.00 output per million tokens (median across 5 API providers). Claude Sonnet 5.5 costs $2.00 input / $10.00 output per million tokens (official Anthropic API price). At a typical mix of three input tokens to one output token, that is $3.44 per million tokens for GPT-5 Chat versus $4.00 for Claude Sonnet 5.5 (1.2× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers both models yet. GPT-5 Chat has not been scored yet and Claude Sonnet 5.5 has an ECI of 166.7.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-5 Chat and Claude Sonnet 5.5 yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Note that GPT-5 Chat does not support tool calling, which most coding agents need.
Which has the bigger context window?
Claude Sonnet 5.5 has the largest context window at 1,000,000 tokens, against 400,000 for GPT-5 Chat. Maximum output per response: GPT-5 Chat up to 128,000, Claude Sonnet 5.5 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GPT-5 Chat accepts text and images; Claude Sonnet 5.5 accepts text, images and PDFs. Claude Sonnet 5.5 handles the widest range of inputs.
Are any of these open source?
No. GPT-5 Chat and Claude Sonnet 5.5 are proprietary and only available through APIs and apps.
Which is newer?
Claude Sonnet 5.5 is the newest, released Sep 28, 2026. GPT-5 Chat came out Aug 7, 2025. Knowledge cutoff: GPT-5 Chat Sep 30, 2024, Claude Sonnet 5.5 Jun 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 Nov 2, 2026.
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