What does password entropy mean?
Password entropy is a way to estimate how difficult a password may be to guess. It is usually based on how long the password is, how many possible characters it uses and how random it is.
Password entropy estimates how many possible guesses an attacker may need before finding the password.
Why password entropy matters
Entropy matters because short or predictable passwords can be guessed more easily. A password with more possible combinations is usually harder to crack by automated guessing.
However, entropy is not the only security factor. A password can have a decent-looking score and still be unsafe if it is reused, leaked, based on personal information or typed into a fake website.
Generate a stronger password
Use the Password Generator to create random-character passwords or random-word passphrases with a strength estimate.
How password entropy works
In simple terms, password entropy estimates the size of the guessing space. A longer password with a wider set of possible characters usually has more possible combinations.
rough entropy idea =
password length × log2(possible character set size)You do not need to calculate this manually. A password generator can provide a rough estimate, but the number should be treated as guidance rather than a guarantee.
What increases password entropy?
Entropy usually increases when a password is longer, more random and chosen from a larger set of possible characters.
Password entropy examples
The examples below are simplified. Real-world password strength also depends on whether the password appears in leaks, dictionaries or common pattern lists.
| Password type | Example pattern | Likely issue |
|---|---|---|
| Short common word | summer | Very predictable and easy to guess. |
| Common word with substitutions | Summer2026! | Looks stronger, but follows a common pattern. |
| Random characters | Long, mixed random string | Usually stronger if generated randomly and stored safely. |
| Random-word passphrase | Several unrelated random words | Can be strong and easier to remember if the words are truly random. |
Password entropy vs password strength
Password entropy is part of password strength, but it is not the whole story. Password strength also depends on whether the password is unique, stored safely and protected by good account security.
| Concept | What it means | What it misses |
|---|---|---|
| Password entropy | How unpredictable the password may be mathematically. | Reuse, phishing, breaches and unsafe storage. |
| Password strength | A wider practical view of how safe the password is. | Still cannot guarantee account safety by itself. |
For practical advice, read the Strong Password glossary page after it is created.
Practical password entropy tips
- Use longer passwords or passphrases.
- Use truly random generation where possible.
- Avoid names, birthdays, addresses and obvious words.
- Do not reuse passwords across accounts.
- Store passwords in a trusted password manager.
- Use multi-factor authentication where available.
- Change passwords that have been exposed in a breach.
Length and randomness usually matter more than making a short password look complicated.
Limitations of entropy estimates
Entropy estimates are useful, but they are not perfect. A tool may estimate strength based on length and character variety, while an attacker may use leaked password lists, common patterns and personal information.
For example, a password based on a football team, pet name or date may look varied but still be predictable to someone with personal information.
How to generate a higher-entropy password
- Open the Password Generator.
- Choose random characters or a random-word passphrase.
- Use enough length for the account’s requirements.
- Copy the result into a trusted password manager.
- Use a different generated password for every account.
A generated password is only useful if you store it securely and do not reuse it.
Password entropy FAQs
Is password entropy the same as password strength?
No. Entropy is one part of password strength, but real security also depends on uniqueness, safe storage, account protection and whether the password has been leaked.
Does adding symbols always make a password strong?
Not always. Symbols help when the password is random, but predictable substitutions such as “@” for “a” are common and easier to guess.
Are passphrases strong?
They can be strong if they are long and made from randomly chosen words. A predictable phrase or quote is not the same as a random passphrase.
What tool can generate a strong password?
Use the Password Generator to create a random password or passphrase.