Short answer
“ChatGPT 5” can refer to the ChatGPT product or be shorthand for an OpenAI model. This comparison is specifically about the OpenAI GPT-5 API model (gpt-5; snapshot gpt-5-2025-08-07) and Anthropic Claude Sonnet 5.5 (claude-sonnet-5-5)—not ChatGPT and Claude subscription plans.
There is an important availability caveat: as of November 12, 2026, OpenAI marks GPT-5 as deprecated and recommends its latest model instead. Its API model page still lists GPT-5’s identifier, specifications, and prices, but that does not guarantee availability for every account or make it a sound default for a new deployment. Anthropic lists Sonnet 5.5 as active and its latest Sonnet model. (developers.openai.com)
For a new production integration, don’t choose deprecated GPT-5 solely because its listed input rate is lower. Confirm that your account can use it, and evaluate the current model you intend to deploy. If you are maintaining a system already pinned to GPT-5, compare its actual results and API costs with Sonnet 5.5 before migrating.
API comparison
| OpenAI GPT-5 | Claude Sonnet 5.5 | |
|---|---|---|
| API model ID | gpt-5 (snapshot: gpt-5-2025-08-07) |
claude-sonnet-5-5 |
| Provider-listed status | Deprecated | Active; latest Sonnet model |
| Standard input price | $1.25 per million tokens | $2 per million tokens |
| Standard output price | $10 per million tokens | $10 per million tokens |
| Context window | 400,000 tokens | 1,000,000 tokens |
| Maximum output | 128,000 tokens | 128,000 tokens |
| Documented controls or features | Reasoning-effort settings; function calling and structured outputs | Adaptive thinking, on by default; effort control |
These are the providers’ published API model details, checked November 12, 2026. GPT-5’s model page lists its prices and features while also labeling the model deprecated. Sonnet 5.5’s page lists its model ID, prices, limits, active status, and adaptive-thinking details. These specifications do not establish which model performs better on a particular workload. (developers.openai.com)
What the differences mean in production
Status is the biggest distinction for a new deployment. GPT-5 is a deprecated model, so verify availability and migration implications before building around it. Sonnet 5.5 is listed as active. If you need to compare GPT-5 with a successor, treat that as a separate model comparison rather than assuming GPT-5’s features, prices, or results carry over. (developers.openai.com)
The listed output prices are equal; GPT-5’s listed input price is lower. On the headline rates, GPT-5 costs less for input tokens, while both models list output at $10 per million tokens. Your total API bill depends on the input/output mix and how many tokens the task actually uses—not just the input rate.
Sonnet 5.5 lists the larger context window. Its one-million-token context may be relevant when a request must include a large amount of material. A larger context limit alone does not establish better results, and it does not mean every request should use the full window.
The documented controls differ, but they are not a quality ranking. OpenAI documents reasoning-effort settings and function calling and structured outputs for GPT-5. Anthropic documents adaptive thinking and effort control for Sonnet 5.5, and describes the model for coding, agent, and enterprise workloads. These are provider-documented capabilities, not evidence that one model will be more accurate or reliable for your application. (developers.openai.com)
Example API cost
For a simple comparison, assume 100,000 input tokens and 10,000 output tokens in one request, with standard listed rates and no other adjustments:
- GPT-5:
(100,000 × $1.25 + 10,000 × $10) ÷ 1,000,000= $0.225. - Claude Sonnet 5.5:
(100,000 × $2 + 10,000 × $10) ÷ 1,000,000= $0.30.
This is a calculation from the providers’ listed per-million-token rates, not a measured workload result. It excludes any usage or pricing conditions beyond those rates. For your own estimate, substitute your expected input and output token counts and check the provider’s current pricing for the API channel you use. (developers.openai.com)
How to decide
- Confirm the product and model. These figures compare API models, not consumer ChatGPT or Claude subscription plans.
- Check GPT-5 availability before considering it. The API documentation marks it deprecated. If you are starting a new integration, evaluate an active model rather than assuming the deprecated listing will remain usable.
- Test on representative tasks. Run the same prompts, tools, and success criteria where possible. Score task completion, correctness, required human edits, latency, and total tokens, including retries and tool calls.
- Compare cost per successful result. Apply the rates for the exact model and API channel to measured input and output usage. A cheaper input token rate does not by itself establish a lower cost for completed work.
Bottom line: GPT-5 and Claude Sonnet 5.5 are not an even-status choice for a new production API: OpenAI marks GPT-5 deprecated, while Anthropic lists Sonnet 5.5 as active. GPT-5’s listed input rate is lower, their listed output rates are equal, and Sonnet 5.5 has the larger documented context window. Confirm GPT-5 availability if you maintain an existing integration; otherwise evaluate active models for a new deployment.