了解词元并计算词元数量

Gemini 和其他生成式 AI 模型会以一种称为“token”的粒度处理输入和输出。

对于 Gemini 模型，一个 token 大致相当于 4 个字符。 100 个 token 大约相当于 60-80 个英文单词。

令牌简介

词元可以是单个字符（例如 z），也可以是整个字词（例如 cat）。长字词会被拆分为多个 token。模型使用的所有 token 的集合称为词汇，将文本拆分为 token 的过程称为 token 化。

启用结算功能后，对 Gemini API 的调用费用部分取决于输入和输出 token 的数量，因此了解如何计算 token 数量会很有帮助。

统计 token 数量

Gemini API 的所有输入和输出（包括文本、图片文件和其他非文本模态）都会进行分词。

您可以通过以下方式统计令牌数量：

  • 使用请求的输入调用 count_tokens。返回仅输入中的词元总数。在发送输入之前调用此方法，以检查请求的大小。

  • 在互动响应中使用 usage。返回输入 (total_input_tokens)、输出 (total_output_tokens)、思考 (total_thought_tokens)、缓存内容 (total_cached_tokens)、工具使用 (total_tool_use_tokens) 和总计 (total_tokens) 的 token 数。

统计文本 token

Python

# This will only work for SDK newer than 2.0.0
from google import genai

client = genai.Client()
prompt = "The quick brown fox jumps over the lazy dog."

# Count tokens before sending
total_tokens = client.models.count_tokens(
    model="gemini-3.8-flash",
    contents=prompt
)
print("total_tokens:", total_tokens.total_tokens)

# Get usage from interaction
interaction = client.interactions.create(
    model="gemini-3.8-flash",
    input=prompt
)
print(interaction.usage)

JavaScript

// This will only work for SDK newer than 2.0.0
import { GoogleGenAI } from '@google/genai';

const client = new GoogleGenAI({});
const prompt = "The quick brown fox jumps over the lazy dog.";

// Count tokens before sending
const countResponse = await client.models.countTokens({
    model: "gemini-3.8-flash",
    contents: prompt,
});
console.log(countResponse.totalTokens);

// Get usage from interaction
const interaction = await client.interactions.create({
    model: "gemini-3.8-flash",
    input: prompt,
});
console.log(interaction.usage);

Java

import com.google.genai.Client;
import com.google.genai.gaos.models.interactions.CreateModelInteraction;
import com.google.genai.gaos.models.interactions.Interaction;
import com.google.genai.gaos.models.interactions.InteractionsInput;
import com.google.genai.gaos.models.interactions.Model;
import com.google.genai.gaos.models.interactions.Usage;
import com.google.genai.gaos.models.operations.CreateInteractionRequestBody;

Client client = new Client();

CreateModelInteraction params =
    CreateModelInteraction.builder()
        .model(Model.of("gemini-3.8-flash"))
        .input(InteractionsInput.of("Calculate tokens for this message."))
        .build();

Interaction interaction =
    client.interactions.create(CreateInteractionRequestBody.of(params)).interaction().get();

if (interaction.usage().isPresent()) {
  Usage usage = interaction.usage().get();
  System.out.println("Input tokens: " + usage.totalInputTokens().orElse(0));
  System.out.println("Output tokens: " + usage.totalOutputTokens().orElse(0));
}

REST

# Specifies the API revision to avoid breaking changes when they become default
curl -X POST "https://generativelanguage.googleapis.com/v1beta/models/gemini-3.8-flash:countTokens" \
  -H "x-goog-api-key: $GEMINI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"contents": [{"parts": [{"text": "The quick brown fox."}]}]}'

统计多轮对话的 token 数量

使用 previous_interaction_id 统计整个对话历史记录中的 token 数量：

Python

# This will only work for SDK newer than 2.0.0
# First interaction
interaction1 = client.interactions.create(
    model="gemini-3.8-flash",
    input="Hi, my name is Bob"
)

# Second interaction continues the conversation
interaction2 = client.interactions.create(
    model="gemini-3.8-flash",
    input="What's my name?",
    previous_interaction_id=interaction1.id
)

# Usage includes tokens from both turns
print(f"Input tokens: {interaction2.usage.total_input_tokens}")
print(f"Output tokens: {interaction2.usage.total_output_tokens}")
print(f"Total tokens: {interaction2.usage.total_tokens}")

JavaScript

// This will only work for SDK newer than 2.0.0
// First interaction
const interaction1 = await client.interactions.create({
    model: "gemini-3.8-flash",
    input: "Hi, my name is Bob"
});

// Second interaction continues the conversation
const interaction2 = await client.interactions.create({
    model: "gemini-3.8-flash",
    input: "What's my name?",
    previous_interaction_id: interaction1.id
});

console.log(`Input tokens: ${interaction2.usage.total_input_tokens}`);
console.log(`Output tokens: ${interaction2.usage.total_output_tokens}`);

Java

import com.google.genai.Client;
import com.google.genai.gaos.models.interactions.CreateModelInteraction;
import com.google.genai.gaos.models.interactions.Interaction;
import com.google.genai.gaos.models.interactions.InteractionsInput;
import com.google.genai.gaos.models.interactions.Model;
import com.google.genai.gaos.models.interactions.Usage;
import com.google.genai.gaos.models.operations.CreateInteractionRequestBody;

Client client = new Client();

CreateModelInteraction params =
    CreateModelInteraction.builder()
        .model(Model.of("gemini-3.8-flash"))
        .input(InteractionsInput.of("Calculate tokens for this message."))
        .build();

Interaction interaction =
    client.interactions.create(CreateInteractionRequestBody.of(params)).interaction().get();

if (interaction.usage().isPresent()) {
  Usage usage = interaction.usage().get();
  System.out.println("Input tokens: " + usage.totalInputTokens().orElse(0));
  System.out.println("Output tokens: " + usage.totalOutputTokens().orElse(0));
}

统计多模态 token

Gemini API 的所有输入内容（包括图片、视频和音频）都会被标记化。 有关分词的关键点：

  • 图片：如果图片的两个尺寸均小于或等于 384 像素，则计为 258 个 token。较大的图片会被平铺为 768x768 像素的图块，每个图块计为 258 个 token。
  • 视频：每秒 263 个 token（适用于静态处理）。对于代理处理，token 用量各不相同。请参阅按处理模式划分的视频令牌使用情况。
  • 音频：每秒 32 个 token

图片 token

Python

# This will only work for SDK newer than 2.0.0
uploaded_file = client.files.upload(file="path/to/image.jpg")

# Count tokens for image + text
total_tokens = client.models.count_tokens(
    model="gemini-3.8-flash",
    contents=["Tell me about this image", uploaded_file]
)
print(f"Total tokens: {total_tokens}")

# Generate with image
interaction = client.interactions.create(
    model="gemini-3.8-flash",
    input=[
        {"type": "text", "text": "Tell me about this image"},
        {"type": "image", "uri": uploaded_file.uri, "mime_type": uploaded_file.mime_type}
    ]
)
print(interaction.usage)

JavaScript

// This will only work for SDK newer than 2.0.0
const uploadedFile = await client.files.upload({
    file: "path/to/image.jpg",
    config: { mimeType: "image/jpeg" }
});

// Count tokens
const countResponse = await client.models.countTokens({
    model: "gemini-3.8-flash",
    contents: [
        { text: "Tell me about this image" },
        { fileData: { fileUri: uploadedFile.uri, mimeType: uploadedFile.mimeType } }
    ]
});
console.log(countResponse.totalTokens);

Java

import com.google.genai.Client;
import com.google.genai.gaos.models.interactions.CreateModelInteraction;
import com.google.genai.gaos.models.interactions.Interaction;
import com.google.genai.gaos.models.interactions.InteractionsInput;
import com.google.genai.gaos.models.interactions.Model;
import com.google.genai.gaos.models.interactions.Usage;
import com.google.genai.gaos.models.operations.CreateInteractionRequestBody;

Client client = new Client();

CreateModelInteraction params =
    CreateModelInteraction.builder()
        .model(Model.of("gemini-3.8-flash"))
        .input(InteractionsInput.of("Calculate tokens for this message."))
        .build();

Interaction interaction =
    client.interactions.create(CreateInteractionRequestBody.of(params)).interaction().get();

if (interaction.usage().isPresent()) {
  Usage usage = interaction.usage().get();
  System.out.println("Input tokens: " + usage.totalInputTokens().orElse(0));
  System.out.println("Output tokens: " + usage.totalOutputTokens().orElse(0));
}

内嵌数据示例：

Python

# This will only work for SDK newer than 2.0.0
import base64

with open('image.jpg', 'rb') as f:
    image_bytes = f.read()

interaction = client.interactions.create(
    model="gemini-3.8-flash",
    input=[
        {"type": "text", "text": "Describe this image"},
        {
            "type": "image",
            "data": base64.b64encode(image_bytes).decode('utf-8'),
            "mime_type": "image/jpeg"
        }
    ]
)
print(interaction.usage)

视频 token

Python

# This will only work for SDK newer than 2.0.0
import time

video_file = client.files.upload(file="path/to/video.mp4")

while not video_file.state or video_file.state.name != "ACTIVE":
    print("Processing video...")
    time.sleep(5)
    video_file = client.files.get(name=video_file.name)

# A 60-second video is approximately 100 * 60 = 6,000 tokens
total_tokens = client.models.count_tokens(
    model="gemini-3.8-flash",
    contents=["Summarize this video", video_file]
)
print(f"Total tokens: {total_tokens}")

# Generate with video
interaction = client.interactions.create(
    model="gemini-3.8-flash",
    input=[
        {"type": "text", "text": "Summarize this video"},
        {"type": "video", "uri": video_file.uri, "mime_type": video_file.mime_type}
    ]
)
print(interaction.usage)

按处理模式统计的视频 token 用量

视频的令牌用量取决于处理模式：

处理模式 token 计算 典型用法
静态（默认） 默认情况下约为 100 个 token/秒（低分辨率），或约为 300 个 token/秒（高分辨率）。所有帧均以 1 FPS 的采样率进行采样。 可预测，与视频时长成正比。
智能体 因内容复杂程度而异。模型仅加载回答提示所需的转写和/或帧和/或音频。 长视频内容的 token 数量最多可减少 88%。

在智能体处理模式下，一个小时的讲座在静态模式下可能需要使用约 108 万个令牌，而在智能体处理模式下可能只需要使用约 10.8 万个令牌，具体取决于提示和内容。

如需检查请求的实际令牌用量，请检查 interaction.usage。代理视频令牌会在以下字段中报告：

  • 初始提示（视频参考 + 用户提示）：total_input_tokens
  • 导航思维：total_thought_tokens
  • 按需加载转写、帧和音频：total_tool_use_tokens
  • 最终答案：total_output_tokens

音频令牌

Python

# This will only work for SDK newer than 2.0.0
audio_file = client.files.upload(file="path/to/audio.mp3")

# A 60-second audio clip is approximately 32 * 60 = 1,920 tokens
total_tokens = client.models.count_tokens(
    model="gemini-3.8-flash",
    contents=["Transcribe this audio", audio_file]
)
print(f"Total tokens: {total_tokens}")

# Generate with audio
interaction = client.interactions.create(
    model="gemini-3.8-flash",
    input=[
        {"type": "text", "text": "Transcribe this audio"},
        {"type": "audio", "uri": audio_file.uri, "mime_type": audio_file.mime_type}
    ]
)
print(interaction.usage)

统计系统指令 token

系统指令计为输入 token：

Python

# This will only work for SDK newer than 2.0.0
interaction = client.interactions.create(
    model="gemini-3.8-flash",
    input="Hello!",
    system_instruction="You are a helpful assistant who speaks like a pirate."
)

# system_instruction tokens included in total_input_tokens
print(f"Input tokens: {interaction.usage.total_input_tokens}")

统计工具 token

工具（函数、代码执行、Google 搜索）也会计入：

Python

# This will only work for SDK newer than 2.0.0
tools = [
    {
        "type": "function",
        "name": "get_weather",
        "description": "Get current weather",
        "parameters": {
            "type": "object",
            "properties": {
                "location": {"type": "string"}
            }
        }
    }
]

interaction = client.interactions.create(
    model="gemini-3.8-flash",
    input="What's the weather in Tokyo?",
    tools=tools
)

print(f"Input tokens: {interaction.usage.total_input_tokens}")
print(f"Tool use tokens: {interaction.usage.total_tool_use_tokens}")

上下文窗口

每种 Gemini 模型都有其可处理的词元数上限。上下文窗口定义了输入和输出 token 的总限制。

以编程方式获取上下文窗口大小

Python

# This will only work for SDK newer than 2.0.0
model_info = client.models.get(model="gemini-3.8-flash")
print(f"Input token limit: {model_info.input_token_limit}")
print(f"Output token limit: {model_info.output_token_limit}")

JavaScript

// This will only work for SDK newer than 2.0.0
const modelInfo = await client.models.get({ model: "gemini-3.8-flash" });
console.log(`Input token limit: ${modelInfo.inputTokenLimit}`);
console.log(`Output token limit: ${modelInfo.outputTokenLimit}`);

Java

import com.google.genai.Client;
import com.google.genai.gaos.models.interactions.CreateModelInteraction;
import com.google.genai.gaos.models.interactions.Interaction;
import com.google.genai.gaos.models.interactions.InteractionsInput;
import com.google.genai.gaos.models.interactions.Model;
import com.google.genai.gaos.models.interactions.Usage;
import com.google.genai.gaos.models.operations.CreateInteractionRequestBody;

Client client = new Client();

CreateModelInteraction params =
    CreateModelInteraction.builder()
        .model(Model.of("gemini-3.8-flash"))
        .input(InteractionsInput.of("Calculate tokens for this message."))
        .build();

Interaction interaction =
    client.interactions.create(CreateInteractionRequestBody.of(params)).interaction().get();

if (interaction.usage().isPresent()) {
  Usage usage = interaction.usage().get();
  System.out.println("Input tokens: " + usage.totalInputTokens().orElse(0));
  System.out.println("Output tokens: " + usage.totalOutputTokens().orElse(0));
}

在模型页面上查找上下文窗口大小。

后续步骤