Token counting

Generative AI models break down text data into units called tokens for processing. The way text data is converted into tokens depends on the tokenizer used. A token can be characters, words, or phrases. Each model has a maximum number of tokens that it can handle in a prompt and response. This page shows you how to get an estimate of the token count and the number of billable characters for a prompt.

Supported models

The following multimodal models support getting an estimate of the prompt token count:

  • gemini-1.5-flash-001
  • gemini-1.5-pro-001
  • gemini-1.0-pro-002
  • gemini-1.0-pro-vision-001

To learn more about model versions, see Gemini model versions and lifecycle.

Get the token count for a prompt

You can get the token count estimate and the number of billable characters for a prompt by using the Vertex AI API.

Python

To learn how to install or update the Vertex AI SDK for Python, see Install the Vertex AI SDK for Python. For more information, see the Python API reference documentation. 

import vertexai
from vertexai.generative_models import GenerativeModel

# TODO(developer): Update and un-comment below line
# project_id = "PROJECT_ID"

vertexai.init(project=project_id, location="us-central1")

model = GenerativeModel(model_name="gemini-1.0-pro-002")

prompt = "Why is the sky blue?"

# Prompt tokens count
response = model.count_tokens(prompt)
print(f"Prompt Token Count: {response.total_tokens}")
print(f"Prompt Character Count: {response.total_billable_characters}")

# Send text to Gemini
response = model.generate_content(prompt)

# Response tokens count
usage_metadata = response.usage_metadata
print(f"Prompt Token Count: {usage_metadata.prompt_token_count}")
print(f"Candidates Token Count: {usage_metadata.candidates_token_count}")
print(f"Total Token Count: {usage_metadata.total_token_count}")

Java

Before trying this sample, follow the Java setup instructions in the Vertex AI quickstart using client libraries. For more information, see the Vertex AI Java API reference documentation.

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

import com.google.cloud.vertexai.VertexAI;
import com.google.cloud.vertexai.api.CountTokensResponse;
import com.google.cloud.vertexai.api.GenerateContentResponse;
import com.google.cloud.vertexai.generativeai.GenerativeModel;
import java.io.IOException;

public class GetTokenCount {
  public static void main(String[] args) throws IOException {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-google-cloud-project-id";
    String location = "us-central1";
    String modelName = "gemini-1.5-flash-001";

    getTokenCount(projectId, location, modelName);
  }

  // Gets the number of tokens for the prompt and the model's response.
  public static int getTokenCount(String projectId, String location, String modelName)
      throws IOException {
    // Initialize client that will be used to send requests.
    // This client only needs to be created once, and can be reused for multiple requests.
    try (VertexAI vertexAI = new VertexAI(projectId, location)) {
      GenerativeModel model = new GenerativeModel(modelName, vertexAI);

      String textPrompt = "Why is the sky blue?";
      CountTokensResponse response = model.countTokens(textPrompt);

      int promptTokenCount = response.getTotalTokens();
      int promptCharCount = response.getTotalBillableCharacters();

      System.out.println("Prompt token Count: " + promptTokenCount);
      System.out.println("Prompt billable character count: " + promptCharCount);

      GenerateContentResponse contentResponse = model.generateContent(textPrompt);

      int tokenCount = contentResponse.getUsageMetadata().getPromptTokenCount();
      int candidateTokenCount = contentResponse.getUsageMetadata().getCandidatesTokenCount();
      int totalTokenCount = contentResponse.getUsageMetadata().getTotalTokenCount();

      System.out.println("Prompt token Count: " + tokenCount);
      System.out.println("Candidate Token Count: " + candidateTokenCount);
      System.out.println("Total token Count: " + totalTokenCount);

      return promptTokenCount;
    }
  }
}

Node.js

Before trying this sample, follow the Node.js setup instructions in the Vertex AI quickstart using client libraries. For more information, see the Vertex AI Node.js API reference documentation.

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment. 

const {VertexAI} = require('@google-cloud/vertexai');

/**
 * TODO(developer): Update these variables before running the sample.
 */
async function countTokens(
  projectId = 'PROJECT_ID',
  location = 'us-central1',
  model = 'gemini-1.5-flash-001'
) {
  // Initialize Vertex with your Cloud project and location
  const vertexAI = new VertexAI({project: projectId, location: location});

  // Instantiate the model
  const generativeModel = vertexAI.getGenerativeModel({
    model: model,
  });

  const req = {
    contents: [{role: 'user', parts: [{text: 'How are you doing today?'}]}],
  };

  const countTokensResp = await generativeModel.countTokens(req);
  console.log('count tokens response: ', countTokensResp);
}

REST

To get the token count and the number of billable characters for a prompt by using the Vertex AI API, send a POST request to the publisher model endpoint.

Before using any of the request data, make the following replacements:

  • LOCATION: The region to process the request. Available options include the following:

    Click to expand available regions

    • us-central1
    • us-west4
    • northamerica-northeast1
    • us-east4
    • us-west1
    • asia-northeast3
    • asia-southeast1
    • asia-northeast1
  • PROJECT_ID: Your project ID.
  • MODEL_ID: The model ID of the multimodal model that you want to use.
  • ROLE: The role in a conversation associated with the content. Specifying a role is required even in singleturn use cases. Acceptable values include the following:
    • USER: Specifies content that's sent by you.
  • TEXT: The text instructions to include in the prompt.
  • NAME: The name of the function to call.
  • DESCRIPTION: Description and purpose of the function.

HTTP method and URL: 

POST https://LOCATION-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/publishers/google/models/MODEL_ID:countTokens

Request JSON body: 

{
  "contents": [{
    "role": "ROLE",
    "parts": [{
      "text": "TEXT"
    }]
  }],
  "system_instruction": {
    "role": "ROLE",
    "parts": [{
      "text": "TEXT"
    }]
  }
  "tools": [{
    "function_declarations": [
      {
        "name": "NAME",
        "description": "DESCRIPTION",
        "parameters": {
          "type": "OBJECT",
          "properties": {
            "location": {
              "type": "TYPE",
              "description": "DESCRIPTION"
            }
          },
          "required": [
            "location"
          ]
        }
      }
    ]
  }]
}

To send your request, choose one of these options:

curl

Save the request body in a file named request.json, and execute the following command: 

curl -X POST \
     -H "Authorization: Bearer $(gcloud auth print-access-token)" \
     -H "Content-Type: application/json; charset=utf-8" \
     -d @request.json \
     "https://LOCATION-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/publishers/google/models/MODEL_ID:countTokens"

PowerShell

Save the request body in a file named request.json, and execute the following command: 

$cred = gcloud auth print-access-token
$headers = @{ "Authorization" = "Bearer $cred" }

Invoke-WebRequest `
    -Method POST `
    -Headers $headers `
    -ContentType: "application/json; charset=utf-8" `
    -InFile request.json `
    -Uri "https://LOCATION-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/publishers/google/models/MODEL_ID:countTokens" | Select-Object -Expand Content

You should receive a JSON response similar to the following.

Example curl command for text with image or video:

MODEL_ID="gemini-1.0-pro-vision"
PROJECT_ID="my-project"
TEXT="Provide a summary with about two sentences for the following article."
REGION="us-central1"

curl \
-X POST \
-H "Authorization: Bearer $(gcloud auth print-access-token)" \
-H "Content-Type: application/json" \
https://${REGION}-aiplatform.googleapis.com/v1/projects/${PROJECT_ID}/locations/${REGION}/publishers/google/models/${MODEL_ID}:countTokens -d \
$'{
    "contents": [{
      "role": "user",
      "parts": [
        {
          "file_data": {
            "file_uri": "gs://cloud-samples-data/generative-ai/video/pixel8.mp4",
            "mime_type": "video/mp4"
          }
        },
        {
          "text": "'"$TEXT"'"
        }]
    }]
 }'

Example curl command for text only:

MODEL_ID="gemini-1.0-pro-vision"
PROJECT_ID="my-project"
TEXT="Provide a summary with about two sentences for the following article."
REGION="us-central1"

curl \
-X POST \
-H "Authorization: Bearer $(gcloud auth print-access-token)" \
-H "Content-Type: application/json" \
https://${REGION}-aiplatform.googleapis.com/v1/projects/${PROJECT_ID}/locations/${REGION}/publishers/google/models/${MODEL_ID}:countTokens -d \
$'{
  "contents": [{
      "role": "user",
      "parts": [{
        "text": "'"$TEXT"'"
      }]
    }]
 }'

Pricing and quota

There is no charge or quota restriction for using the CountTokens API. The maximum quota for the CountTokens API is 3000 requests per minute.

What's next