Why tokens matter
Models have a limit on how many tokens they can handle at once, and API prices are quoted per million tokens, with output usually costing more than input.
Estimating
Divide characters by four, or words by 0.75. A 44-character, 9-word sentence is about 11 to 12 tokens. The Token Counter does both estimates, and the LLM Cost Calculator turns counts into cost.
Common misunderstanding
A token is not a word. Code, numbers and non-English text usually need more tokens, and each model has its own tokenizer, so counts differ. See how to estimate the token count of a prompt.