BCBetter Calculators

Password Strength by Length Calculator

Calculate the number of possible password combinations based on length and character set size.

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Enter your values and click Calculate

How It Works

The total number of possible passwords equals charset size raised to the power of the password length (charset^length). Because this number grows astronomically fast — a 20-character password from a 95-character set produces roughly 10^39 combinations — the result is displayed as a power of 10 using the formula length × log₁₀(charset). Entropy in bits is calculated as length × log₂(charset), which is the standard measure used in security research and password policy guidelines. Each additional bit of entropy doubles the number of guesses an attacker must try. A password below 28 bits is trivially crackable; 60+ bits provides solid resistance against modern brute-force attacks; and 128+ bits is considered effectively unbreakable with current computing technology.

Examples

4-digit PIN
Length 4, digits only (10 chars).
Result: 10,000 combinations (10^4), 13.3 bits — Very Weak.
12-char mixed password
Length 12, 72-character set.
Result: Approximately 10^22 combinations, 75.5 bits — Strong.
20-char full ASCII
Length 20, full printable ASCII (95 chars).
Result: Approximately 10^39 combinations, 131.1 bits — Extremely Strong.

Frequently Asked Questions

What is entropy in bits?
Entropy measures unpredictability in password generation. Each additional bit of entropy doubles the number of guesses an attacker must make. Security researchers generally consider 80+ bits very strong and 128+ bits effectively uncrackable with current technology.
Why does length matter more than complexity?
Adding one character multiplies the total combinations by the entire charset size. Going from 8 to 12 characters with a 72-character set raises the combinations by a factor of 72^4 (roughly 27 million), whereas swapping letters for symbols typically only changes the charset size from 52 to 62 — a much smaller gain.
What character set should I use for my password?
The more types of characters you include — lowercase, uppercase, digits, and symbols — the larger the charset and the stronger the password. Using the full printable ASCII set (95 characters) gives you the strongest possible pool. Most modern password managers generate passwords using this full set by default.

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