Stop guessing your AI API bill: a quick guide to token cost math

You can ship an LLM feature in an afternoon. Figuring out what it costs to run usually happens later, when the invoice shows up and someone asks why. A few minutes of token math up front avoids most of that. Here is how the pricing works and how to estimate it. Tokens, not words Providers bill per token, not per word or per request. A token is about 4 characters of English, so "Hello world" is roughly 3 tokens and 750 words lands near 1,000 tokens. Input and output are billed separa...