Password Length Calculator

Choose an alphabet size and target bits to calculate the minimum uniformly random password length; this model does not estimate human-chosen password strength.

Target theoretical bits

Alphabet size

Preset

—Minimum length under a uniform independent-draw model

Sensitive values stay in this browser page. Theoretical entropy/search-space math assumes uniform random generation and is not a crack-time promise for human-chosen passwords. Use a reputable password manager for real account storage.

Entropy & crack-time scenario audit

Turn target entropy and pool size into explicit search-space and time assumptions.

Security model

Guess rate / second

Scenario	Guesses / sec	Worst case	Average case

Modern password guidance without false certainty

keeps password/passphrase generation and review browser-local while shifting guidance toward length, uniqueness, common-password blocking, password-manager compatibility, MFA, and compromise-driven changes rather than arbitrary composition rules or guaranteed crack-time claims.

Security boundary

A local meter can flag obvious patterns but cannot prove that a password is safe, unused elsewhere, or absent from every breach corpus. Do not paste sensitive production password exports into batch tools; generate unique secrets locally and store them in an appropriate password manager.

Practical guide and verification

Length targets depend on how passwords are generated

A uniformly random password from a known alphabet has quantifiable search space, while a human-chosen password of the same length can be far more predictable. Do not apply random-password entropy formulas directly to memorable patterns or reused phrases.

Attack-rate assumptions can change results by many orders of magnitude

Offline cracking speed depends on the password hash, hardware, cost parameters and attacker resources. Treat crack-time output as a scenario based on the chosen rate rather than a universal promise of how long a real account will resist.

Online authentication is governed by rate limits too

For a well-designed online service, throttling, lockout, MFA and anomaly detection can dominate raw password search speed. Password length still matters, but the offline and online threat models should not be mixed into one number.

Longer is usually more robust than complicated composition rules

When a system allows it, increasing a randomly generated password or passphrase length expands the search space without relying on hard-to-remember substitution tricks. Check the destination maximum length and supported characters before generating a credential.

Use the calculator to set a policy, then verify the generator

After choosing a target entropy or length, confirm that the actual password generator uses the assumed alphabet and secure randomness. A policy estimate is only valid when the issued credentials match the generation model used in the calculation.