Password Entropy Calculator

Frequently Asked Questions

What entropy should I target for different account types?

Security practitioners generally target 60+ bits for standard accounts, 80+ bits for privileged accounts, and 128+ bits for encryption keys. NIST SP 800-63B recommends minimum 8-character passwords with breach checking.

Why does this not account for human-chosen password patterns?

This models a theoretically random password. Human passwords contain patterns (names, dates, keyboard walks) that crackers exploit, making actual entropy much lower. Treat results as a generous upper bound for human-chosen passwords.

What is the difference between offline and online cracking rates?

Online cracking is limited by server rate limiting (thousands of attempts/s). Offline cracking happens after a hash database is stolen, at GPU speeds. Bcrypt at high cost factors slows offline cracking to thousands of guesses/s.

Is a passphrase more secure than a random password?

A 4-word Diceware passphrase yields ~51 bits; a random 12-character alphanumeric gives ~71 bits. A 6-word passphrase (~77 bits) or 16-character random password (~95 bits) are both strong for high-security needs.

Provided by AllCalculators.io
Free online calculators for everyday. No registration required.

Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

JavaScript is required to use the interactive calculator above. The questions and answers below remain readable without JavaScript.

How It Works

Password strength is measured in bits of entropy, which is the base-2 logarithm of how many guesses an attacker must try on average. The formula is E = L x log2(R), where L is the password length and R is the size of the character pool. A 12-character password using lowercase + uppercase + digits draws from a pool of 62 characters, so each position adds log2(62) approximately equal to 5.95 bits, giving about 71 bits total.

Crack time assumes an attacker tries half the keyspace on average: (2^E / 2) / guesses-per-second. The calculator shows both an offline rate (a fast GPU rig cracking a breached hash, approximately 10^10/s) and a throttled online rate (a login form with rate limiting, approximately 10^3/s). This model assumes a random password - human-chosen passwords contain patterns that crack tools exploit, making the actual entropy much lower than this calculation suggests.

Use Cases

Security engineers and IT administrators use this calculator to:

Compare password policies (minimum length, required character classes) by entropy rather than arbitrary complexity rules.

Demonstrate to management or users why length matters far more than adding a single special character.

Validate that generated passwords from a password manager or provisioning script meet a minimum entropy target (60 bits for ordinary accounts, 80+ bits for privileged accounts).

Educate development teams on why bcrypt, Argon2, or scrypt with high cost factors matter more than raw entropy for stored passwords.

Evaluate passphrase policies - four Diceware words yield about 51 bits, comparable to a 9-character fully random mixed-case alphanumeric password.

Tips

Never type a real password into any web tool - enter the composition only (length and character classes); this calculator never receives your actual secret.

Length beats complexity - a 20-character lowercase password has 94 bits of entropy; a 12-character mixed-case+symbol password has about 78 bits. Every added character multiplies the keyspace by the full pool size.

Dictionary words have near-zero entropy - a 10-letter common word drawn from a 200,000-word dictionary has only about 18 bits regardless of how long it looks.

Unique passwords matter as much as strong ones - credential stuffing attacks try breached password-hash pairs across all sites; a 100-bit entropy password is worthless if it is reused and appears in a breach database.

Use a password manager - it generates and stores 20+ character random passwords per site, removing the human bottleneck and making both length and uniqueness effortless.

FAQ

What entropy should I target for different account types?

NIST SP 800-63B does not mandate entropy thresholds but recommends minimum 8-character passwords (with breach checking) for ordinary accounts. Security practitioners generally target 60+ bits for standard accounts, 80+ bits for privileged or administrative accounts, and 128+ bits for encryption keys and secrets.

Why does this not account for human-chosen password patterns?

This calculator models a theoretically random password drawn uniformly from the pool. Real human passwords contain names, dates, keyboard walks (qwerty, 12345), and leetspeak substitutions that crackers exploit with rule-based attacks. Treat the result as a generous upper bound for human-chosen passwords; for random passwords it is accurate.

What is the difference between offline and online cracking rates?

Online cracking is limited by the login server's rate limiting - typically hundreds to thousands of attempts per second before lockout. Offline cracking occurs after a password hash database is stolen; the attacker runs on their own hardware at speeds limited only by the hashing algorithm and GPU count. Bcrypt at cost 12 cuts GPU cracking to thousands of guesses per second even with fast hardware.

Is a passphrase more secure than a random password?

A four-word Diceware passphrase from a 7,776-word list has about 51 bits of entropy. A random 12-character alphanumeric password has about 71 bits. The passphrase is weaker in raw entropy but far easier to remember and type. For high-security needs, a 6-word Diceware passphrase (77 bits) or a random 16-character password (95 bits) are both strong choices.

Password Entropy Calculator

Frequently Asked Questions

Related Networking & IT Calculators