Password Strength Checker
Evaluate password resilience with entropy scoring, brute-force crack time estimates, and NIST SP 800-63B security compliance checks.
Input Parameters
Live Result
// ========================================================================== // PASSWORD SECURITY AUDIT REPORT // ========================================================================== Score: 100% (Extremely Strong) Entropy: 124.8 bits Length: 19 characters Character Pool: 95 possible characters Estimated Crack: Centuries (Centillions of years - Mathematically Unbreakable) (at 100B hashes/sec) NIST SP 800-63B: COMPLIANT Vulnerabilities: None
Details
Steps
Analyzed character set distribution: Lowercase (✓), Uppercase (✓), Numbers (✓), Symbols (✓) -> Total pool size N = 95.
Calculated Shannon Information Entropy: E = 19 × log₂(95) = 125 bits (adjusted to 124.8 bits after pattern penalties).
Modeled brute-force keyspace: 2^124.8 = 3.70e+37 combinations against 100B guesses/sec.
Estimated time to crack 50% search space: Centuries (Centillions of years - Mathematically Unbreakable). Assigned security grade: Extremely Strong (100%).
Quick Answer & Understanding Your Result
A Password Strength Checker evaluates password entropy in bits, brute-force cracking duration, and dictionary vulnerability risks to ensure your credentials meet modern NIST SP 800-63B authentication benchmarks.
Core Password Evaluation Metrics
- Shannon Information Entropy: Measures true cryptographic unpredictability: E = L * log2(N) bits, accounting for character set pool sizes.
- Brute-Force Attack Modeling: Simulates exhaustion time across attacker capabilities from web rate-limited attacks (1,000/s) to enterprise GPU cracking clusters (100 Billion/s).
- Common Leak & Dictionary Detection: Flags exposed passwords found in major data breaches (e.g. RockYou, HaveIBeenPwned).
- Pattern & Repetition Penalties: Deducts security scores for sequential characters (123, abc) and repetitive keystroke patterns.
NIST SP 800-63B Modern Guidelines
- Minimum 8 characters for user-created passwords (12-16+ recommended for critical accounts).
- Favoring long multi-word passphrases over complex, hard-to-remember short passwords.
Type your password into the input box above to audit its strength, entropy, and crack time in 0ms.
Formula & Calculation Logic
Mathematical FormulaEvaluation pipeline:
- L is password length, N is character pool size (up to 95 chars for full ASCII).
- Calculates total combinations (2^E) and estimates average 50% keyspace brute-force search time.
Step-by-Step Guide
Enter Password String
Type or paste your password into the evaluation field.
Select Attacker Hardware Profile
Choose the threat model (e.g. 100B hashes/sec for offline GPU rig or 1K/sec for web attack).
Review Entropy & Vulnerability Breakdown
Check entropy score, detected character pools, and any repetition warnings.
Apply Security Recommendations
Increase length and use random passphrases if crack time or entropy is insufficient.
Worked Examples Table
| Example | Input Values | Calculated Result | Explanation |
|---|---|---|---|
| Strong 19-Character Mixed Passphrase | Combines upper, lower, digits, and symbols with 19 characters, providing over 95 bits of entropy. | ||
| Common Weak Leaked Password | Identified in common dictionary leaks, vulnerable to immediate automated cracking. |
Frequently Asked Questions
Evidence-Based Methodology & Authoritative References
NIST Special Publication 800-63B - Digital Identity Guidelines
OWASP Authentication & Password Storage Cheat Sheet
Standard: ISO / W3C / IETF Authoritative Domain Standard
Formula: E = L × log2(N), T_crack = 2^(E - 1) / GuessesPerSecond
Last Reviewed: August 21, 2026
Primary Source: NIST Special Publication 800-63B - Digital Identity Guidelines
Reference Document: OWASP Authentication & Password Storage Cheat Sheet
Computation Privacy: 100% client-side 0ms computation, zero data retention
Calculated results are modeled based on standard scientific and mathematical formulas. Please verify with domain-specific technical documentation for specialized applications.
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Calculated results are modeled based on standard scientific and mathematical formulas. Please verify with domain-specific technical documentation for specialized applications.