How to count Claude tokens

Step-by-step guide for developers using the Messages API.

1. 1

   Copy your user message (and optional system prompt) into the tokenizer.

2. 2

   Select the exact model ID you will call in production.

3. 3

   Click Count tokens and note input_tokens.

4. 4

   Add tool definitions, images, or PDFs in your real API call — they add tokens not shown in plain text alone.

5. 5

   Leave headroom below the model context window for the model's reply.

Open token counter