At the time this document has been written, each new ChatGPT account includes 3 months of free API usage. Following that, requests to ChatGPT API are charged on a pay-for-what-you-use basis.
Fees are currently based on the total tokens used for each request made to the API. Current fees are $0.002 per 1000 tokens used.
A token can represent a single character or a whole word, depending on the language and context. As a rough guide, 1 token is approximately 4 characters for English text.
For up-to-date pricing, please see the OpenAI website.
Here you can see the number of tokens used for each request sent to the AI. The total tokens used is the sum of tokens used for the prompt and tokens used for the response.
With each request sent to the AI, your assistant persona, prompt, and content field text all count towards your total token usage.