At a glance
| Spec | GPT-5 | GPT-5.5 |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Input / 1M | $0.50 | $1.50 |
| Output / 1M | $2.00 | $6.00 |
| Context | 128K | 128K |
| Extended thinking | No | No |
The verdict
For most teams, GPT-5.5 is the better default if cost matters, while GPT-5 earns its premium on the hardest tasks. Pick based on whether a wrong answer is expensive enough to justify the higher price.
GPT-5: where it wins
GPT-5 brings state-of-the-art language understanding, generation, and tool use, including the Codex coding variant. Native function calling and JSON mode make it a strong fit for structured, tool-driven applications.
Best for: function calling and tool use, structured json output.
GPT-5.5: where it wins
GPT-5.5 steps up reasoning and reliability over the base GPT-5 line, aimed at harder tasks that still want OpenAI's tool-use ergonomics. A good middle ground when GPT-5 isn't quite enough but you want to stay in the OpenAI ecosystem.
Best for: harder reasoning within the openai ecosystem, complex tool-use workflows.
Cost in practice
On a typical request with 2,000 input and 800 output tokens, GPT-5 costs about $0.00260 and GPT-5.5 about $0.00780. Plug in your own numbers with the cost calculator.
Run both behind one API
Switch between GPT-5 and GPT-5.5 by changing one line. $1 free to start.
Start FreeFAQ
Is GPT-5 or GPT-5.5 cheaper?
GPT-5 is cheaper on input tokens ($0.50 vs $1.50 per 1M). Output pricing follows the same order.
Which is better for coding, GPT-5 or GPT-5.5?
For most teams, GPT-5.5 is the better default if cost matters, while GPT-5 earns its premium on the hardest tasks. Pick based on whether a wrong answer is expensive enough to justify the higher price.
Can I use both GPT-5 and GPT-5.5 with one API?
Yes. Through KissAPI both run behind one OpenAI-compatible endpoint, so you can route between GPT-5 and GPT-5.5 by changing only the model id.