What is password entropy?

Password entropy is a measure of how unpredictable a password is, measured in bits. It is calculated as log2(S^L), where S is the character set size and L is the password length. Higher entropy means more possible passwords and a harder crack.

How long would it take to crack my password?

This depends entirely on the attacker's hardware and whether they have a hashed version of your password (offline attack) or must guess through a login form (online attack). Online attacks (limited by network and lockouts) make even short passwords viable. Offline attacks on leaked hashes require 80+ bit entropy passwords to be genuinely infeasible.

Is a password that passes a strength meter actually strong?

Not necessarily. Most password strength meters use simple rules (length > 8, has symbol, has number) that can be satisfied by weak passwords like "P@ssword1". True strength requires randomness and length — properties that simple visual meters often don't fully capture.

What is the difference between a strong password and a memorable one?

Strong passwords prioritise entropy (length + randomness). Memorable passwords prioritise human recallability. Passphrases are the best tool when you need both — they achieve high entropy while remaining memorable through the structure of natural language words.

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How Strong Is My Password? Understanding Password Strength

Password strength is not a feeling — it is a calculation. This guide explains what entropy means, how crack times are estimated, and what actually makes a password strong or weak. Learn to evaluate any password objectively, and see how to generate genuinely strong ones.

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Plain English explanation of password entropy

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Crack time estimates for common password types

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The factors that actually matter for password security

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How to use this tool

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After reading this guide, use the FixTools Password Generator to create passwords that meet the strength criteria described here.

How It Works

Step-by-step guide to how strong is my password? understanding password strength:

1
Calculate your password's character space
Lowercase only: 26 chars. + Uppercase: 52. + Numbers: 62. + Common symbols: 94. The larger the character space and the longer the password, the more possible combinations exist.
2
Estimate entropy in bits
Entropy = log2(character_space ^ length). 60+ bits is good. 80+ bits is strong. 100+ bits is very strong. An 8-character password with all character types has about 52 bits — borderline.
3
Check for known patterns
Does your password contain dictionary words, dates, name + number combos, or common substitutions? If yes, the actual security is far lower than the entropy calculation suggests because attackers target these patterns first.
4
Generate a replacement if needed
If your analysis reveals your password is weak, use the FixTools Password Generator to create a replacement that is genuinely strong by length, entropy, and randomness.

Real-world examples

Common situations where this approach makes a real difference:

Security audit preparation

A security-conscious user reads this guide before conducting a personal credential audit, using the entropy framework to categorise all their existing passwords by true strength and prioritising which to replace first.

Team security training

A security manager uses this guide as the basis for a 15-minute team training session on password security, explaining entropy and crack times in plain English to non-technical staff.

Password policy design

A developer designing password requirements for a new application uses this guide to set requirements based on actual entropy targets (minimum 60 bits) rather than arbitrary complexity rules that frustrate users without significantly improving security.

When to use this guide

Read this guide to understand whether your existing passwords are truly strong, or before creating important passwords to know what to aim for.

Pro tips

Get better results with these expert suggestions:

Length is the most important factor

Each additional character of length increases the number of possible passwords exponentially. A 20-character lowercase-only password is vastly stronger than an 8-character password with every symbol type.

Avoid substitutions and patterns

"P@ssw0rd" is not strong. Attackers know about substitution patterns (@ for a, 0 for o, 3 for e) and they are included in all modern password dictionaries. These modifications provide almost no additional security.

Complexity alone is not enough without length

An 8-character password that uses all character types can be cracked in hours with modern hardware. The same password extended to 16 characters would take decades. Always prioritise length first, then complexity.