Token counting enables you to determine the number of tokens in a message before sending it to Claude, helping you make informed decisions about your prompts and usage. With token counting, you can

  • Proactively manage rate limits and costs
  • Make smart model routing decisions
  • Optimize prompts to be a specific length

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How to count message tokens

The token counting endpoint accepts the same structured list of inputs for creating a message, including support for system prompts, tools, images, and PDFs. The response contains the total number of input tokens.

The token count should be considered an estimate. In some cases, the actual number of input tokens used when creating a message may differ by a small amount.

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Supported models

The token counting endpoint supports the following models:

  • Claude Opus 4
  • Claude Sonnet 4
  • Claude Sonnet 3.7
  • Claude Sonnet 3.5
  • Claude Haiku 3.5
  • Claude Haiku 3
  • Claude Opus 3

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Count tokens in basic messages

import anthropic

client = anthropic.Anthropic()

response = client.messages.count_tokens(
    model="claude-opus-4-20250514",
    system="You are a scientist",
    messages=[{
        "role": "user",
        "content": "Hello, Claude"
    }],
)

print(response.json())
JSON
{ "input_tokens": 14 }

​
Count tokens in messages with tools

Server tool token counts only apply to the first sampling call.

import anthropic

client = anthropic.Anthropic()

response = client.messages.count_tokens(
    model="claude-opus-4-20250514",
    tools=[
        {
            "name": "get_weather",
            "description": "Get the current weather in a given location",
            "input_schema": {
                "type": "object",
                "properties": {
                    "location": {
                        "type": "string",
                        "description": "The city and state, e.g. San Francisco, CA",
                    }
                },
                "required": ["location"],
            },
        }
    ],
    messages=[{"role": "user", "content": "What's the weather like in San Francisco?"}]
)

print(response.json())
JSON
{ "input_tokens": 403 }

​
Count tokens in messages with images

#!/bin/sh

IMAGE_URL="https://upload.wikimedia.org/wikipedia/commons/a/a7/Camponotus_flavomarginatus_ant.jpg"
IMAGE_MEDIA_TYPE="image/jpeg"
IMAGE_BASE64=$(curl "$IMAGE_URL" | base64)

curl https://api.anthropic.com/v1/messages/count_tokens \
     --header "x-api-key: $ANTHROPIC_API_KEY" \
     --header "anthropic-version: 2023-06-01" \
     --header "content-type: application/json" \
     --data \
'{
    "model": "claude-opus-4-20250514",
    "messages": [
        {"role": "user", "content": [
            {"type": "image", "source": {
                "type": "base64",
                "media_type": "'$IMAGE_MEDIA_TYPE'",
                "data": "'$IMAGE_BASE64'"
            }},
            {"type": "text", "text": "Describe this image"}
        ]}
    ]
}'
JSON
{ "input_tokens": 1551 }

​
Count tokens in messages with extended thinking

See here for more details about how the context window is calculated with extended thinking

  • Thinking blocks from previous assistant turns are ignored and do not count toward your input tokens
  • Current assistant turn thinking does count toward your input tokens
curl https://api.anthropic.com/v1/messages/count_tokens \
    --header "x-api-key: $ANTHROPIC_API_KEY" \
    --header "content-type: application/json" \
    --header "anthropic-version: 2023-06-01" \
    --data '{
      "model": "claude-opus-4-20250514",
      "thinking": {
        "type": "enabled",
        "budget_tokens": 16000
      },
      "messages": [
        {
          "role": "user",
          "content": "Are there an infinite number of prime numbers such that n mod 4 == 3?"
        },
        {
          "role": "assistant",
          "content": [
            {
              "type": "thinking",
              "thinking": "This is a nice number theory question. Lets think about it step by step...",
              "signature": "EuYBCkQYAiJAgCs1le6/Pol5Z4/JMomVOouGrWdhYNsH3ukzUECbB6iWrSQtsQuRHJID6lWV..."
            },
            {
              "type": "text",
              "text": "Yes, there are infinitely many prime numbers p such that p mod 4 = 3..."
            }
          ]
        },
        {
          "role": "user",
          "content": "Can you write a formal proof?"
        }
      ]
    }'
JSON
{ "input_tokens": 88 }

​
Count tokens in messages with PDFs

Token counting supports PDFs with the same limitations as the Messages API.

curl https://api.anthropic.com/v1/messages/count_tokens \
    --header "x-api-key: $ANTHROPIC_API_KEY" \
    --header "content-type: application/json" \
    --header "anthropic-version: 2023-06-01" \
    --data '{
      "model": "claude-opus-4-20250514",
      "messages": [{
        "role": "user",
        "content": [
          {
            "type": "document",
            "source": {
              "type": "base64",
              "media_type": "application/pdf",
              "data": "'$(base64 -i document.pdf)'"
            }
          },
          {
            "type": "text",
            "text": "Please summarize this document."
          }
        ]
      }]
    }'
JSON
{ "input_tokens": 2188 }

​
Pricing and rate limits

Token counting is free to use but subject to requests per minute rate limits based on your usage tier. If you need higher limits, contact sales through the Anthropic Console.

Usage tierRequests per minute (RPM)
1100
22,000
34,000
48,000

Token counting and message creation have separate and independent rate limits — usage of one does not count against the limits of the other.

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FAQ