Everyday calculator

Password Strength Checker, Crack Time & Security Score

Check your password strength and see estimated crack time, character analysis, and specific suggestions to make it stronger. 100% local, never sent to any server.

Published by CalcMesh · Reviewed against primary-source formulas

How CalcMesh evaluates password strength

We estimate strength from length and character variety, the factors that drive entropy. According to the National Institute of Standards and Technology guideline SP 800-63B, length matters more than forced complexity, and long passphrases are encouraged.

All evaluation runs entirely in your browser, your password is never sent to a server, and the entropy model we use is described in our methodology.

Password Security Guide

Password Best Practices

Length over complexity: A 16-character password with only lowercase letters has more entropy than a random 8-character password with all character types.
Unique per site: Never reuse passwords. If one account is breached, all accounts with the same password are compromised.
Avoid personal info: Names, birthdays, pet names, and addresses are among the first things attackers try.
No common patterns: Avoid "Password1!", "qwerty", "abc123", and keyboard patterns like "zxcvbn".

The Passphrase Approach

Instead of a complex password like "J#7kQ!9m", consider a passphrase of 4-6 random words:

"maple-candle-orbit-frozen" (easy to remember, very strong)
"correct horse battery staple" (the classic XKCD example)

Random word passphrases are both stronger and easier to remember than short complex passwords. The key is using truly random words, not song lyrics or famous quotes.

Password Managers

A password manager is the best way to maintain unique, strong passwords for every account. Recommended options:

1Password: User-friendly, family sharing, travel mode
Bitwarden: Open source, free tier available
KeePassXC: Fully offline, open source

Enable Two-Factor Authentication

Even a strong password can be stolen in a data breach. Two-factor authentication (2FA) adds a second layer of security. Prefer authenticator apps (like Authy or Google Authenticator) over SMS codes, as SMS can be intercepted via SIM swapping.

Note: This tool provides a rough estimate of password strength. Real-world attack resistance depends on the hashing algorithm used by the service and the attacker's resources.

Methodology & Assumptions

This calculator implements standard formulas drawn from primary-source authorities. Values are point-in-time estimates; consult a licensed professional for high-stakes decisions. See the per-input definitions and source citations below.

How this works

Computations are deterministic and run client-side, no inputs leave your browser. Formulas are derived from standard published formulas for the calculator's domain (mortgage, taxes, energy, conversions, etc.). When the underlying agency publishes updated rates or thresholds we refresh defaults and update the page's lastmod timestamp.

Frequently Asked Questions

Is it safe to type my password into this tool?

Yes. This tool runs entirely in your browser using JavaScript. Your password is never sent to any server, never stored, and never leaves your device. You can verify this by disconnecting from the internet and using the tool, it works completely offline. The source code is visible in your browser developer tools for full transparency.

What makes a strong password?

A strong password has at least 12 characters and combines uppercase letters, lowercase letters, numbers, and special symbols. Length is the single most important factor, a 16-character password with just lowercase letters is often stronger than an 8-character password with all character types. Avoid dictionary words, personal information, and common patterns like "123" or "abc".

Should I use a passphrase instead of a password?

Passphrases (such as "correct-horse-battery-staple") are an excellent approach. They are longer, easier to remember, and can be very strong. A 4-word passphrase from a large word list provides about 44 bits of entropy per word, making it comparable to a random 12-character password. The key is using truly random words, not a meaningful sentence.

Do I need a password manager?

A password manager is strongly recommended. It generates unique, strong passwords for every account and remembers them for you. This means you only need to memorize one master password. Reusing passwords across sites is one of the biggest security risks, if one site is breached, attackers try those credentials on other sites. Popular options include 1Password, Bitwarden, and KeePassXC.

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This page identifies the inputs, method, and limitations behind its estimates. Calculator outputs are not professional advice and should be checked against the relevant primary source for a consequential decision. This calculator's formula and defaults are drawn from standard published sources for its domain, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.

Inputs, defaults, and authoritative sources
Input	Default	Source / authority
All inputs	Domain-typical defaults	Editorial methodology, CalcMesh 2026