Password Entropy Calculator
Calculate Shannon entropy bits, character pool sizes, and realistic GPU brute force cracking times according to NIST standards.
Entropy Mathematics (NIST SP 800-63B)
Brute Force Cracking Resistance
The Mathematics of Password Security
For decades, users were told to replace letters with numbers (such as "P@ssw0rd!"). Attackers and automated cracking tools like Hashcat and John the Ripper easily account for these rule-based mutations. Shannon information entropy provides the true mathematical benchmark of cryptographic resilience.
Security Applications
- ✓Enterprise Cybersecurity Password Policies
Evaluate corporate IAM password complexity requirements against real-world Shannon bit thresholds to defend Active Directory and Okta domains.
- ✓Master Password & Password Manager Audit
Verify that your master password for 1Password, Bitwarden, or KeePass surpasses 80+ bits of entropy to resist offline dictionary and hashcat attacks.
- ✓Crypto Wallet Passphrase Generation
Test seed phrases and mnemonic passphrases to ensure they provide cryptographic resistance against state-sponsored quantum and ASIC miners.
- ✓Developer API Secret & Token Validation
Ensure generated bearer tokens, webhook secrets, and database encryption keys have sufficient randomness to thwart cryptanalysis.
Key Capabilities
Shannon Entropy Mathematical Model
Computes exact bits of entropy using `E = L * log2(R)` where L represents character length and R represents character set cardinality.
Real-World GPU Cracking Benchmarks
Simulates brute force attempts across online throttled services, single Nvidia RTX 4090 GPUs (160 GH/s), and multi-GPU enterprise cracking rigs.
NIST SP 800-63B Compliance
Identifies bad practices like repetitive substrings and predictable sequences while favoring length over arbitrary symbol substitutions.
100% Client-Side Privacy
Evaluations execute exclusively in browser memory. No passwords, hashes, or keystrokes ever traverse the network.
Frequently Asked Questions
What is password entropy and how many bits is safe?
Password entropy is a mathematical measure of how unpredictable a password is, expressed in bits. Fewer than 28 bits is extremely weak and cracked instantly. 36 to 59 bits offers moderate defense against online attacks. 60 to 79 bits is strong. 80 to 128+ bits provides military and cryptographic-grade resistance against massive offline GPU clusters.
Why is a long passphrase better than a short complex password?
Because entropy scales linearly with length (`L`) and logarithmically with character pool (`R`). An 18-character passphrase using only lowercase letters gives `18 * log2(26) = 84.6 bits` of entropy, whereas an 8-character password with symbols gives only `8 * log2(95) = 52.5 bits`. Length provides exponentially greater defense against brute force.
How fast can modern GPUs crack passwords?
A single modern Nvidia RTX 4090 GPU running Hashcat can compute over 160 billion MD5 or NTLM hashes every second. An 8-GPU cluster reaches over 1.3 trillion hashes per second, cracking simple 8-character alphanumeric passwords in minutes.
Is it safe to test my real password on this website?
Yes. This tool operates 100% client-side in your local browser JavaScript engine. It does not send HTTP requests, does not connect to any third-party API, and does not retain logs. You can even disconnect your internet connection and test it completely offline.
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