Entropy Calculator – Calculate Password & Data Entropy in Bits

Measure the true randomness and security of your passwords with our Entropy Calculator. Enter your password or data string to calculate entropy in bits — helping security professionals and developers assess cryptographic strength.

Password or Passphrase

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Use Custom Character Set

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Enter a password and click Calculate to see entropy analysis

About Password Entropy

Entropy measures the randomness and unpredictability of a password. Higher entropy means better security against brute-force attacks.

Formula: Entropy = L × log₂(N), where L is password length and N is the size of the character set.

Character Set Sizes:

• Lowercase only: 26
• + Uppercase: 52
• + Numbers: 62
• + Symbols: ~94

Entropy Guidelines:

• < 28 bits: Very Weak
• 28-36 bits: Weak
• 36-60 bits: Moderate
• 60-80 bits: Strong
• > 80 bits: Very Strong

How Password Entropy Calculation Works

Enter Your Password

Type or paste your password or passphrase into the input field for analysis.

Analyze Character Set

The calculator identifies lowercase, uppercase, numbers, and symbols to determine character set size.

Get Entropy Score

View entropy in bits, strength rating, and estimated time to crack using brute force.

Why Use This Entropy Calculator?

✓Scientific Security Measurement

Uses information theory to measure true password randomness, not just length or complexity rules.

✓Real-World Crack Time Estimates

Shows how long it would take to crack your password at 1 trillion guesses per second.

✓Secure Password Generator

Generate cryptographically strong passwords with 8, 12, 16, or 20 characters instantly.

✓Custom Character Set Support

Define your own character set for specialized entropy calculations.

✓Shannon Entropy Mode

Calculate Shannon entropy for any data string, useful for cryptography and data analysis.

Password Entropy Formula

Entropy = L × log₂(N)

Where:

L = Password length (characters)
N = Character set size
log₂ = Base-2 logarithm

Character Set Sizes:

Numbers only (0-9): 10
Lowercase (a-z): 26
Alphanumeric: 62
Full ASCII printable: ~94

Frequently Asked Questions About Password Entropy

What is password entropy?

Password entropy measures the randomness and unpredictability of a password in bits. Higher entropy means more possible combinations and better resistance to brute-force attacks.

How many bits of entropy is considered secure?

For most purposes, 60+ bits is strong, 80+ bits is very strong. NIST recommends at least 80 bits for high-security applications. Below 36 bits is considered weak.

Is a longer password always better?

Generally yes, but character variety matters too. A 12-character password with mixed case, numbers, and symbols often has more entropy than a 15-character lowercase-only password.

What makes a password have high entropy?

High entropy comes from length, character variety (lowercase, uppercase, numbers, symbols), and true randomness. Avoid patterns, dictionary words, and predictable substitutions.

How is entropy different from password strength meters?

Entropy is a mathematical measure based on information theory. Many strength meters use arbitrary rules. Entropy gives a more accurate measure of brute-force resistance.

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