🔐 Password Strength: Calculator

Test any password for entropy, estimated crack time, and a security checklist — 100% private.

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This tool estimates password strength using entropy (randomness) math and common pattern checks. It runs 100% client-side in your browser — nothing you type is ever transmitted, logged, or stored anywhere.

PASSWORD STRENGTH
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Entropy
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Length
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Crack Time (offline)
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Crack Time (online)
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How Password Strength Is Measured

Password strength is commonly measured using entropy — a measure, in bits, of how unpredictable a password is. Entropy depends on two things: how long the password is, and how large the pool of possible characters used in it is (lowercase letters, uppercase letters, numbers, and symbols).

Entropy (bits) = Length × log₂(Character Pool Size)

A longer password drawn from a larger character set has exponentially more possible combinations, which is why length matters more than most people expect — a 16-character password using only lowercase letters can be far stronger than an 8-character password crammed with symbols.

Why "Crack Time" Estimates Matter

This calculator estimates how long a brute-force attack would take under two scenarios: a slow, rate-limited online attack (e.g., against a login form with lockouts) and a fast offline attack (e.g., against a leaked, hashed password database using powerful hardware). These are simplified estimates for education — real-world crack times vary enormously with the specific hashing algorithm and attacker resources.

Tips for Stronger Passwords

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❓ Frequently Asked Questions

Is my password sent anywhere when I use this tool?
No. All calculations happen entirely in your browser using JavaScript. Your input is never transmitted to any server, logged, or stored — you can even test this offline after the page loads.
What is password entropy?
Entropy measures password unpredictability in bits, based on length and character variety. Higher entropy means exponentially more possible combinations an attacker would need to try.
Why is length more important than complexity?
Each additional character multiplies the total number of possible passwords by the size of your character pool, so length increases the search space exponentially — often more effectively than adding a few symbols to a short password.
Are these crack time estimates exact?
No, they're simplified educational estimates based on common guess-rate assumptions. Real attacks depend heavily on the specific hashing algorithm used to store the password and the attacker's available computing power.
Should I use a password manager instead of memorizing passwords?
Yes — most security experts recommend using a reputable password manager to generate and store long, unique, random passwords for every account, so you never need to reuse or memorize weak ones.

🏆 About This Tool — Accuracy & Trust

🔒 Data Privacy: All calculations run entirely within your browser using JavaScript. Nothing you enter here is ever transmitted to our servers, stored, sold, or shared.

📐 Accuracy Note: This tool uses standard, widely published formulas and guidelines. Results are estimates for informational purposes; for financial, medical, or engineering decisions, consult a licensed professional.

📅 Last Updated: September 2026.