Count the exact number of tokens used by a prompt before sending it to an LLM.
Token counting estimates how many tokens a prompt will consume. Most modern LLMs use BPE tokenization where ~4 characters equals one token for English text. Knowing exact token usage helps stay within context limits and predict costs.
Token Estimate
tokens ≈ character_count / chars_per_token
Exact token counts depend on the specific tokenizer (GPT uses tiktoken, Claude uses its own). The 4-char rule is a reliable heuristic for English but varies by language.
Special characters, code, and non-English text often tokenize less efficiently (more tokens per character), so the actual count may be higher than the estimate.