Tokens & Pricing
Output tokens (completion tokens)
The tokens the model generates back to you. Output tokens almost always cost more per token than input tokens — often 3–5× more — because generating text is the expensive part.
Example
The model replies with a 200-word summary (~270 output tokens). If input is $3 per million tokens and output is $15 per million, this one call costs about $0.016 for input plus $0.004 for output — small, until you make it a million times a day.
Related terms
Token
The unit AI models read and write, and the unit you're billed in. A token is a chunk of text — often a word, a piece of a word, or a punctuation mark. Models don't see letters or words; they see tokens.
Input tokens (prompt tokens)
The tokens you send into the model — your prompt, the instructions, any documents or history you include. You pay for these whether or not the answer is any good.
Reasoning tokens
Extra output tokens some models generate as internal "thinking" before they produce a final answer. You're billed for them, but you usually never see them — they're the model working through the problem.
Cost per 1K tokens
The standard way pricing is quoted: dollars per 1,000 tokens, listed separately for input and output. Providers increasingly quote per million tokens, but the per-1K figure is still the mental unit for estimating a call.