Calculator Suite

Password Strength Tester

Analyze password security with entropy calculation, pattern detection, and actionable recommendations. All analysis happens locally in your browser.

Check for common words and passwords

Detect patterns like 'qwerty' or '123456'

Find repeated character sequences

Enter a Password
Start typing a password to see real-time strength analysis, entropy calculation, and security recommendations.
All analysis happens locally in your browser
No passwords are sent to any server
Real-time feedback as you type
The Math of Password Security
How we calculate entropy and crack time

Entropy Formula (Bits)

E=L×log⁡2(R)E = L \times \log_2(R)

L = Password Length

R = Pool Size (e.g., 26 for lowercase, 62 for alphanumeric)

Every extra bit doubles the search space for an attacker.

Estimated Crack Time

Time=2EGuesses/Sec\text{Time} = \frac{2^E}{\text{Guesses/Sec}}

We assume a powerful attacker capable of billions of guesses per second.

Building Unbreakable Passwords

Password Entropy is a measure of unpredictability. A password like "Password123" has low entropy because it follows a common pattern. A password like "Tr0ub4dor&3" is better, but a generated string "xK9#mP2$nL" is mathematically much stronger.

Why Length Beats Complexity

Mathematically, adding length is more effective than adding complexity. Adding one character to a 10-character password multiplies the difficulty by the pool size (e.g., ×62\times 62).

Weak Patterns to Avoid

  • Running sequences (12345, abcd)
  • Keyboard walks (qwerty, asdf)
  • Common substitutions (@ for a, 1 for i)
  • Personal info (birthdays, pet names)

Strong Habits

  • Use Passphrases (4 random words)
  • Use a Password Manager
  • Enable 2FA (Two-Factor Auth)
  • Unique passwords for every site

3 Key Checks (The "SOP")

  1. Length Check: Is it at least 12 characters? (16+ is ideal for high security).
  2. Dictionary Check: Can you find any part of it in a dictionary? If yes, it's vulnerable to dictionary attacks.
  3. Uniqueness Check: Have you used this password before? If a site gets breached, recycled passwords compromise all your accounts.

Frequently Asked Questions

Is this password checker safe?

Yes. This tool runs 100% in your browser. Your password is never sent to our servers or Google. We use local JavaScript to calculate entropy.

What is a good entropy score?

Generally, 60+ bits is decent for low-risk accounts. 80+ bits is strong (hard to crack). 100+ bits is often considered "uncrackable" with current technology.

Why are "Passphrases" better?

"CorrectHorseBatteryStaple" is easier to remember than "Tr0ub4dor&3" but actually has higher entropy because of its length (25 chars vs 11).

Curated video guide
Selected YouTube lessons that add context after the calculator, formulas, examples, assumptions, and limitations.

How to Choose a Password

Source: Computerphile on YouTube

Why this video: Selected because Computerphile explains password choice in a practical security education format without harvesting user data.

What it adds: It supplements entropy and crack-time estimates by discussing why predictable human choices weaken passwords.

Use with this calculator: Check a sample pattern in the calculator, then use the video to understand why length and uniqueness matter.

Limits: The video is general security education and cannot audit a specific account, breach history, device, or threat model.