Paste a prompt. The tool estimates token count using a heuristic and shows usage as a gauge against each model's context window. Heuristic only — actual tokens depend on each model's tokenizer (BPE for Claude, tiktoken for OpenAI, SentencePiece for Gemini, etc.). Useful for budget planning, not for billing-precise counts.
Notes on the estimate
- Heuristic: ~4 chars per token for English prose, weighted up for whitespace and punctuation. Real tokenizers vary.
- Code is denser: source code typically uses 3.0-3.5 chars per token. Long identifiers and operators tokenize differently from prose.
- Non-English: CJK and many other languages use significantly more tokens per character. The estimate undercounts here.
- Output budget: the context window is shared between input and output. If you're asking for a 20K-token response, your input budget is correspondingly smaller.
- Vision / files: images and document attachments consume tokens too. This tool only measures text.