Password Entropy Estimator

Calculate how many bits of entropy a password scheme provides and how long brute-forcing it would take.

FreeNo sign-upRuns in your browserMobile-friendly
Sensitive data: everything runs on your device and nothing is sent or stored. Still, avoid entering passwords you currently use on shared or public computers.

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What does the Password Entropy Estimator do?

Entropy measures unpredictability. For randomly generated passwords, entropy H = L × log₂(N), where L is the length and N the number of possible symbols. A 12-character password from all 94 printable ASCII characters has about 78.7 bits; a 6-word passphrase from the 7,776-word Diceware list has about 77.5 bits.

Set the attacker’s guess rate to see what the numbers mean in practice: about 10 billion guesses per second for a GPU rig against a fast hash, thousands for a slow hash like bcrypt, or a handful per minute for a rate-limited login.

How to use the Password Entropy Estimator

  1. Choose “Calculate from settings” and enter length and character set — or “Estimate from a password”.
  2. Set the attacker’s guesses per second.
  3. Read the entropy, combinations and crack times.

Examples

Comparison

8 lowercase letters ≈ 37.6 bits (minutes offline); 16 mixed characters from 94 ≈ 104.9 bits (practically uncrackable).

Common use cases

  • Designing password policies
  • Comparing passwords and passphrases
  • Security training and coursework

Features and benefits

  • Private by design — your data is processed on your device and never uploaded.
  • Free with no account, no watermark and no usage limits.
  • Works on phones, tablets and desktops in any modern browser.

Limitations to know

  • The formula assumes truly random choices. Human-chosen passwords have far less entropy than the formula suggests.

Helpful guides

Frequently asked questions

How many bits are enough?

Around 70–80 bits is strong for most accounts; 100+ bits for high-value secrets.

Why does a word count as one symbol?

For random passphrases, each word is chosen from a list, so entropy per word is log₂(list size).

Is the password sent anywhere?

No, calculation is local.

Embed this tool on your website

Add the free Password Entropy Estimator to your blog or website. Paste the code into your page’s HTML; the tool runs in your visitors’ browsers and stays up to date automatically. Please keep the credit line below the tool.

Free to use on any website. The tool runs inside an iframe served from viptools.pk; nothing your visitors type is sent to your site or ours. Preview the embedded version.

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