Password Strength Calculator - Check Your Password Security Free Online

Free password strength calculator to analyze your password security. Get instant score, entropy analysis, crack time estimation, and improvement suggestions. 100% private - runs locally in your browser.

10 min read

Password Strength Calculator

iAbout This Calculator

Password security is the cornerstone of your digital life, serving as the primary barrier between malicious actors and your personal information, financial accounts, and online identity. Our free Password Strength Calculator analyzes your password in real-time, providing a comprehensive security assessment that goes far beyond simple length checks. The tool evaluates multiple critical factors including character length, character set diversity (uppercase letters, lowercase letters, numbers, and special symbols), sequential patterns, keyboard patterns, repeated characters, and checks against common password dictionaries derived from real-world data breaches. You will receive an instant security score from 0-100, detailed entropy calculation measured in bits, estimated time-to-crack under various attack scenarios, and personalized suggestions to strengthen your password. Understanding your password's vulnerability is crucial in an era where automated attacks can test billions of combinations per second. All analysis is performed entirely within your browser using client-side JavaScript. Your password is never transmitted over the network, stored on any server, or logged anywhere. You can even disconnect from the internet and verify the calculator continues to function, ensuring complete privacy for your most sensitive credentials.

?How to Use

1
Enter your password or passphrase in the secure input field. Analysis begins immediately as you type each character, providing instant feedback on your password's strength evolution.
2
Observe the visual strength meter that fills progressively and changes color based on security level: red indicates a weak password that could be cracked quickly, orange shows fair security with room for improvement, yellow represents good security suitable for less critical accounts, lime green indicates strong security recommended for important accounts, and bright green shows excellent security ideal for high-value targets like banking and email.
3
Review the detailed component breakdown showing individual scores for: password length contribution, uppercase letter usage, lowercase letter presence, numeric digit inclusion, special character utilization, and pattern detection results including keyboard walks, sequential characters, and repeated sequences.
4
Examine the entropy value displayed in bits, which represents the mathematical unpredictability of your password. Higher entropy means exponentially more combinations an attacker must try. Aim for at least 60 bits for general accounts and 80+ bits for critical accounts.
5
Check the estimated crack time displayed for multiple attack scenarios: online attacks with rate limiting, offline attacks against stolen hashes, and GPU-accelerated cracking attempts. This helps contextualize your password's real-world security.
6
Follow the personalized improvement suggestions provided. These recommendations are prioritized by impact, helping you achieve maximum security improvement with minimal changes to your password.

fFormula

\text{Entropy} = L \times \log_2(N)

Password entropy quantifies unpredictability using information theory. The formula multiplies password length (L) by the logarithm base 2 of the character set size (N). Each character type expands the set: lowercase adds 26 possibilities, uppercase adds 26 more, digits add 10, and common symbols add approximately 32, totaling 94 printable ASCII characters. A larger character set dramatically increases entropy. For example, an 8-character lowercase password has 26^8 combinations (about 208 billion), while adding uppercase and numbers increases this to 62^8 (about 218 trillion). The crack time estimation assumes modern attack hardware capable of 10 billion guesses per second for offline attacks, or 1000 guesses per second for online attacks with rate limiting.

L: Password length measured in total characters
N: Character set size (26 for lowercase only, 52 with uppercase, 62 with digits, 94 for full ASCII)
Entropy: Password strength measured in bits of information

Examples

Critically Weak Password

Inputs: password: password123

Score: 15/100 (Critical)

This password appears in virtually every breach database and attacker dictionary. Despite 11 characters, it combines the most common password ('password') with predictable sequential numbers. It would be cracked instantly in any attack regardless of the raw entropy calculation.

Deceptively Weak Password

Inputs: password: P@ssw0rd!

Score: 30/100 (Weak)

While this password uses all character types (uppercase, lowercase, numbers, symbols), it follows the extremely common 'leet speak' substitution pattern. Attackers know to try a->@, s->$, o->0 variations. This password appears in breach databases and would be cracked within seconds.

Fair Password

Inputs: password: MyDog2019!

Score: 45/100 (Fair)

Uses mixed case, numbers, and a symbol, but contains personal information (pet name) and a year pattern (2019). Social engineering or public social media profiles could reveal these details. At 10 characters, it provides moderate protection against random brute force but remains vulnerable to targeted attacks.

Strong Random Password

Inputs: password: T#9kL$mW2vQ@xZ

Score: 92/100 (Excellent)

14 characters with true randomness across all character types. No recognizable patterns, dictionary words, or common substitutions. With approximately 84 bits of entropy, this password would take millions of years to crack even with advanced GPU clusters. Ideal for password manager master passwords.

Excellent Passphrase

Inputs: password: correct-horse-battery-staple-7

Score: 95/100 (Excellent)

This 31-character passphrase demonstrates that length triumphs over complexity. Four random words plus a separator and number create memorable yet highly secure credentials. With over 90 bits of entropy, the astronomical search space makes brute force attacks computationally infeasible for centuries.

Use Cases

Creating New Account Passwords

Before signing up for any online service, test your planned password to ensure it meets modern security standards. Different accounts warrant different security levels: use 'Strong' or higher ratings for email (which often serves as recovery for other accounts), banking, cloud storage, and social media. For less critical accounts, 'Good' may suffice, but never go below 'Fair' for any account.

Password Manager Master Password Verification

Your password manager's master password is the single most important credential you possess, as it protects all your other passwords. Use this calculator to verify it achieves 'Excellent' status with 80+ bits of entropy. Consider using a passphrase of 5-6 random words for this critical credential, as you need to memorize it rather than store it anywhere.

Security Audit and Credential Rotation

IT professionals and security-conscious individuals can audit existing passwords to identify weak credentials requiring immediate rotation. Prioritize accounts with scores below 50 for urgent updates, especially if those passwords were created before you understood modern security practices. Regular audits should be performed quarterly for high-value accounts.

Educational and Training Purposes

Teachers, corporate trainers, and security awareness programs can use this calculator to demonstrate password security concepts interactively. Show participants how adding length versus complexity affects strength scores, demonstrate why common patterns are detected and penalized, and illustrate the exponential relationship between character set size and crack time.

Compliance and Policy Verification

Verify that passwords meet organizational security requirements and compliance frameworks such as NIST 800-63B, PCI-DSS, HIPAA, or SOC 2. Many frameworks now emphasize length over complexity and recommend checking passwords against breach databases. This calculator helps ensure policy compliance before credential deployment.

Post-Breach Password Recovery

After receiving notification of a data breach affecting a service you use, create new passwords and verify they achieve significantly higher security scores than your previous credentials. Assume attackers have your old password and any variations, so create something completely different using this calculator to validate strength.

Frequently Asked Questions

Is my password sent to any server when using this calculator?

Absolutely not. All password analysis is performed locally in your browser using JavaScript. Your password never leaves your device - it is not transmitted to any server, not logged, not stored in cookies, and not sent to analytics services. You can verify this by disconnecting from the internet and testing the calculator, which continues to function fully offline. We designed this tool specifically to ensure complete privacy for your most sensitive credentials.

What exactly is password entropy and why does it matter?

Entropy measures password unpredictability using information theory, expressed in bits. Each bit represents a doubling of the search space an attacker must explore. A password with 40 bits of entropy has 2^40 (about 1 trillion) possible combinations. At 60 bits, that grows to over 1 quintillion combinations. At 80 bits, the combinations exceed the number of atoms on Earth. Higher entropy means exponentially more time and computational resources required for brute force attacks. Modern recommendations suggest 60+ bits for general accounts and 80+ bits for critical accounts.

How accurate is the estimated crack time?

The estimation models several attack scenarios: online attacks assume rate limiting allows roughly 1000 attempts per second, while offline attacks against stolen password hashes assume optimized GPU clusters achieving 10 billion guesses per second. Real-world scenarios vary significantly - some poorly secured services allow faster online attacks, while salted hashes may slow offline attacks. The estimate provides a useful relative comparison between passwords, but should not be considered an absolute guarantee.

Why did my long password score poorly?

Length alone does not guarantee strength. The calculator detects and penalizes: dictionary words in any language, common substitutions (@ for a, 0 for o), keyboard patterns (qwerty, 12345), repeated characters or sequences, dates and years, and passwords appearing in known breach databases. A 20-character password consisting of 'passwordpassword1234' scores far worse than a 12-character truly random string. Focus on both length AND randomness.

What password score should I aim for?

For general, low-risk accounts: 50+ (Good). For important accounts like social media, shopping sites with saved payment info: 70+ (Strong). For critical accounts including email, banking, cloud storage, password manager master passwords: 85+ (Excellent). Your email deserves the highest protection since it typically serves as the recovery mechanism for all other accounts - compromising email often means compromising everything.

Are special characters more important than length?

No - length provides exponentially greater security improvement. Adding special characters increases the character set from 62 to 94 (a 51% increase), while each additional character multiplies the total combinations by the entire character set size. For example, adding one character to a 94-character-set password multiplies combinations by 94x, while adding symbols to an existing password only increases the base. Long passphrases with simple separators often outperform short complex passwords.

Should I use a password generator instead of creating my own?

Yes, for most passwords. Humans are notoriously bad at generating random sequences - we fall into patterns, use memorable substitutions, and incorporate personal information without realizing it. Random password generators produce truly unpredictable credentials. Use this calculator to verify generated passwords meet your requirements, and only create passwords manually when you need something memorable (like a master password), testing thoroughly with this tool.

Why are some common passwords flagged even with mixed characters?

Attackers maintain and continuously update wordlists containing millions of passwords from real data breaches. Common passwords, popular modifications (P@ssw0rd!, Summer2024!), and patterns are tried first in every attack. A password appearing in breach databases will be cracked in seconds regardless of its theoretical entropy. Our calculator checks against common patterns and penalizes passwords that match known attack vectors.

How often should I change my passwords?

Modern security guidance (including NIST 800-63B) no longer recommends periodic password rotation without cause. Instead, change passwords when: you suspect compromise, you receive a breach notification, you shared the password with someone, or you initially set a weak password. Focus on creating strong, unique passwords upfront rather than frequently changing weak ones. However, monitor for breaches using services like HaveIBeenPwned.

What are the most common password mistakes people make?

The top password security mistakes include: reusing passwords across multiple sites, using personal information like names and dates, following predictable patterns like capitalizing only the first letter, appending numbers or years to the end, using common keyboard patterns, choosing passwords that are too short, substituting letters with obvious symbols (@, $, 0, 1, 3), and not using a password manager. Each of these habits makes passwords exponentially easier to crack.

Conclusion

Strong, unique passwords remain your most critical defense against unauthorized access and identity fraud. This Password Strength Calculator provides detailed analysis to understand your password security and identify improvements. Use this tool for every important account, aim for scores above 85 for sensitive credentials, and complement strong passwords with two-factor authentication. Make password security a habitual part of your digital life.

Pro Tips

*Length beats complexity every time: A 20-character password using only lowercase letters (26^20 combinations) is exponentially stronger than an 8-character password using all character types (94^8 combinations). Aim for 16+ characters minimum for important accounts, 12+ for general use.
*Embrace passphrases for memorability: String together 4-6 random, unrelated words with separators (e.g., 'purple-elephant-quantum-bicycle-forest'). These are easier to remember than random characters while providing excellent security. Avoid famous quotes, song lyrics, or phrases that appear in books.
*Never include personal information: Names, birthdays, anniversaries, pet names, addresses, phone numbers, and other personal details are easily discoverable through social media, public records, or social engineering. Attackers build targeted wordlists from this information.
*Use unique passwords everywhere: Password reuse is the number one cause of account compromises. When one service is breached, attackers immediately try those credentials on banking, email, and other high-value targets. Use a password manager to generate and store unique passwords for every account.
*Enable two-factor authentication (2FA) as defense in depth: Even strong passwords can be compromised through phishing, keyloggers, or session hijacking. 2FA provides a critical second barrier. Prefer authenticator apps or hardware keys over SMS-based 2FA when available.
*Respond immediately to breach notifications: When a service reports a data breach, change that password within hours, not days. Also change passwords on any other accounts where you may have reused similar credentials. Assume the worst and act quickly.