Tokens & Pricing
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.
Example
The sentence "Make every token count." is about 5 tokens. A rough rule of thumb for English: 1,000 tokens is roughly 750 words, or about a page and a half.
Related terms
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.
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.
Context window
The maximum number of tokens a model can consider at once — input plus output combined. It's the model's working memory for a single call. Go over it and the request fails or silently drops the oldest content.
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.