How to Get File Size in Node.js: Methods & Best Practices

Learn how to check file size in Node.js using built-in modules like fs and fs.promises. This guide covers synchronous and asynchronous methods with code examples.

When working with files in Node.js, it’s often useful to determine the size of a file — whether for validation, logging, or to enforce upload/download limits. Node.js provides built-in modules to retrieve file metadata, including size, using simple and efficient methods.

In this post, we’ll explore different ways to get the size of a file in Node.js using:

• fs.statSync (synchronous)
• fs.promises.stat (async/await)
• fs.stat (callback-based)

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🛠 Prerequisites

Ensure you have Node.js installed:

node -v

Create a sample file for testing:

echo "Hello, Node.js file size check!" > test.txt

📏 Method 1: Using fs.statSync() (Synchronous)

If you’re working in a script or CLI tool where blocking I/O is acceptable:

const fs = require('fs');

const stats = fs.statSync('test.txt');
console.log(`File size: ${stats.size} bytes`);

📌 stats.size gives the size of the file in bytes.

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🕒 Method 2: Using fs.promises.stat() (Async/Await)

For non-blocking applications, especially servers or services:

const fs = require('fs').promises;

async function getFileSize(filePath) {
  try {
    const stats = await fs.stat(filePath);
    console.log(`File size: ${stats.size} bytes`);
  } catch (err) {
    console.error('Error getting file size:', err);
  }
}

getFileSize('test.txt');

⏳ Method 3: Using fs.stat() with Callbacks

If you’re using traditional Node.js callback patterns:

const fs = require('fs');

fs.stat('test.txt', (err, stats) => {
  if (err) {
    return console.error('Error:', err);
  }
  console.log(`File size: ${stats.size} bytes`);
});

📦 Bonus: Convert Bytes to KB/MB

To display the size in kilobytes or megabytes:

const fileSizeInKB = (bytes) => (bytes / 1024).toFixed(2);
const fileSizeInMB = (bytes) => (bytes / (1024 * 1024)).toFixed(2);

Example:

console.log(`Size: ${fileSizeInKB(stats.size)} KB`);
console.log(`Size: ${fileSizeInMB(stats.size)} MB`);

🧠 Use Cases

• Validating file upload limits
• Logging file statistics
• Monitoring disk usage
• Caching file size in services

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🧪 Conclusion

Node.js makes it easy to retrieve file sizes using its core fs module. Depending on your application type (CLI, API server, async service), choose the appropriate method:

Method	Use Case
fs.statSync	Simple scripts, CLI tools
fs.promises.stat	Modern apps with async/await
fs.stat	Legacy apps or callback patterns

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🔗 Further Reading

• Node.js fs Docs
• Buffer and Streams in Node.js