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パスワードエントロピー計算機

任意のパスワードのエントロピー(ビット数)と強度カテゴリを算出。

はじめに

Password Entropy Calculator — Bits of entropy and strength category for any password. Enter Password length, , , , to get an instant, accurate result.

計算式

Entropy (bits) = length × log₂(charset size), where charset size is the sum of the character sets used (26 lowercase + 26 uppercase + 10 digits + 32 symbols, as applicable). Higher entropy means more possible combinations an attacker must try.

ステップごとの説明

  1. Enter the Password length.
  2. Toggle "Lowercase letters" on or off as needed.
  3. Toggle "Uppercase letters" on or off as needed.
  4. Toggle "Numbers" on or off as needed.
  5. Toggle "Symbols" on or off as needed.
  6. Click Calculate to see your result instantly.

実例

Example: With Password length = 16, Lowercase letters = yes, Uppercase letters = yes, Numbers = yes, Symbols = no, the Password Entropy Calculator gives Charset Size: 62, Entropy Bits: 95.2671, Category: very strong.

よくある質問

What entropy is considered a strong password?
Below 28 bits is weak, 28–35 is moderate, 36–59 is strong, and 60+ bits is considered very strong.
Why does adding symbols increase entropy so much?
Entropy grows with the logarithm of charset size, so expanding the pool of possible characters at each position increases the total number of possible passwords exponentially.
Does length or character variety matter more?
Length has an outsized effect since entropy scales linearly with it — a longer password with a smaller charset often beats a short one with every character type enabled.
What inputs does the Password Entropy Calculator need?
You'll need to provide: Password length, , , , . All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Password Entropy Calculator?
The Password Entropy Calculator applies the formula exactly as calculated — Entropy (bits) = length × log₂(charset size), where charset size is the sum of the character sets used (26 lowercase + 26 uppercase + 10 digits + 32 symbols, as applicable). Higher entropy means more possible combinations an attacker must try. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Password Entropy Calculator free to use?
Yes, the Password Entropy Calculator is completely free, requires no signup, and runs instantly in your browser.

パスワードエントロピー計算機について

The Password Entropy Calculator uses a real, verifiable formula — Entropy (bits) = length × log₂(charset size), where charset size is the sum of the character sets used (26 lowercase + 26 uppercase + 10 digits + 32 symbols, as applicable). Higher entropy means more possible combinations an attacker must try. — so results are accurate every time, not an approximation.