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Entropy Calculator

Calculate Shannon entropy of text

What is Entropy Calculator?

Entropy Calculator is a free online tool that helps you calculate shannon entropy of text. It runs entirely in your browser using client-side JavaScript, so your data stays private and never leaves your device.

When to Use

  • Generating secure credentials, keys, or hashes for your applications
  • Checking or verifying security configurations and encryption settings
  • Learning about cryptographic concepts and security best practices

How to Use

Enter your input in the field above, adjust any settings if available, and click the action button. Results appear instantly—no page reload, no server wait. All processing happens locally in your browser.

Related Tools

Try our Password Strength for related functionality.

Deep Dive: How Entropy Calculator Works

Entropy Calculator is a security-focused tool that helps protect digital assets and sensitive information through proven cryptographic principles and security best practices. In today's threat landscape where data breaches and credential theft are commonplace, understanding and properly implementing security measures is no longer optional—it's a fundamental requirement for any application handling user data. Entropy Calculator operates entirely client-side using your browser's JavaScript engine, meaning sensitive inputs like passwords, secrets, or personal data never traverse the network or touch a remote server. This zero-trust, local-only architecture ensures your confidential information remains completely private and under your control at all times. Security tools like this empower developers, system administrators, and everyday users to implement industry-standard protection without deep cryptographic expertise or expensive infrastructure. Whether you're generating secure credentials, validating security configurations, or testing system hardening, having these capabilities instantly available in your browser dramatically lowers the barrier to good security practices.

Pro Tips

  • Store hashes, not passwords—if your database is compromised, hashed passwords limit the damage
  • Regularly audit your security configurations using checker tools to catch misconfigurations early
  • Understand what entropy actually measures—high entropy means unpredictable, not necessarily strong

Common Mistakes to Avoid

  • Using MD5 or SHA-1 for password storage—these are trivially crackable with modern hardware
  • Trusting client-side entropy calculations as definitive—true randomness requires hardware sources

Frequently Asked Questions

What is Shannon entropy and how do I calculate it for text?
Shannon entropy measures information density in bits per character—higher entropy means more randomness and less predictability. Paste your text into an entropy calculator and it analyzes character frequency distribution to compute entropy. Random passwords score high (4.7+ bits per character), while English text scores lower (3.5-4 bits per character).
How is entropy used to measure password strength?
Password entropy quantifies unpredictability: each additional possible character multiplies the search space. A truly random 8-character password from a 72-character set has about 49 bits of entropy, while a 16-character one has 98 bits. The entropy calculator helps you understand whether your password is genuinely random or containing predictable patterns that reduce security.
What's a good entropy score for a secure password or encryption key?
For passwords, aim for 60+ bits of entropy (roughly a 10-character completely random string with mixed case and numbers). For encryption keys, 128+ bits is the standard minimum. The entropy calculator shows per-character entropy multiplied by length. Note that calculated entropy assumes perfect randomness—any patterns or dictionary words reduce effective entropy.