Password Strength Checker: How Strong Is Your Password?

Type a password to see a strength rating, an estimate of its entropy in bits, how long a fast offline attack might take, and what to improve. Everything runs in your browser and nothing is sent, saved or put in the link.

FreeNo sign-upRuns in your browserUpdated 2 Nov 2026
Tip: test a similar password, not one you use for important accounts.
Your resultLive

Estimates only. Check important results before you rely on them.

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How to use this calculator

  1. Type a password in the box.
  2. Read the strength rating and the entropy estimate.
  3. Check the crack-time estimate.
  4. Follow the tips to improve it.

The formula

Entropy ≈ Length × log2(size of the character set), reduced for repeated characters, sequences, common passwords, words with digits added and plain word phrases. Time to crack = 2^entropy ÷ 2 ÷ 10 billion guesses per second.

Worked example

The 16-character password K9#mV2$xQ7!pL4zR uses 94 possible characters, so it is about 105 bits and rated very strong. The phrase "correct horse battery staple" is made of 4 ordinary words and is estimated at about 52 bits.

Understanding your result

The estimate is a rough guide, not a guarantee. It cannot see your name, birthday or words that are specific to you, which attackers try first. A long random password from a password manager is the best choice, and using a different password for every site matters more than any score.

When to use it

  • Check a password before using it.
  • See why a password is weak.
  • Teach family or staff about password habits.

Assumptions and limits

Your text never leaves the page and is not added to the page address. Still, avoid typing a password you use for a bank or email account into any website.

Frequently asked questions

What makes a password strong?

Length and unpredictability. A long, random password that is unique to one site is the strongest.

Is it safe to type my password here?

The check runs in your browser and nothing is sent, but it is best to test a similar password rather than a real one.

What is entropy?

A measure in bits of how many guesses are needed. Each extra bit doubles the work.

Is a passphrase better?

A passphrase of four or more random words is strong and easy to remember, if the words are chosen randomly.

How often should I change my password?

Change it if you suspect a leak. Otherwise a unique strong password and two-step verification matter more.