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Entropy Calculator

Estimate the entropy and brute-force time of a secret.

What Is a Entropy Calculator?

The Entropy Calculator estimates the entropy of a password, key, or token in bits based on its length and the variety of characters used. It also estimates how long it would take to crack the secret by brute force at 10 billion guesses per second, giving a practical sense of its strength. This free online security tool is useful for password entropy calculator, entropy checker, password entropy estimator. Common use cases include estimating the unpredictability of passwords, tokens, and keys and comparing their theoretical brute-force resistance. It is designed for quick browser-based analysis and development workflows. Security checks are signals rather than guarantees, so production systems should also be validated against current standards and their specific threat model.

How to Use This Entropy Calculator

  1. 1
    Enter the secret to estimateProvide a password, token, or key for analysis.
  2. 2
    Review character diversityCheck the estimated character space used by the input.
  3. 3
    Review entropySee the estimated unpredictability in bits.
  4. 4
    Consider the crack-time estimateUse it as an approximation rather than a guarantee.
  5. 5
    Improve the secretPrefer longer, randomly generated, unique secrets for important systems.

Frequently Asked Questions

For important secrets, aim for 80 bits or more. Values below about 60 bits become increasingly vulnerable to distributed brute-force attacks.
Each additional character multiplies the number of possible combinations exponentially, so length contributes more to entropy than any single character type.
It is an approximation. Actual cracking time depends on the attacker's hardware, but the estimate gives a useful scale of the secret's strength.

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