What Is Password Entropy?
Password entropy is a scientific measurement of how unpredictable a password is. It's expressed in bits and represents the number of guesses an attacker would need to crack your password through brute force. The higher the entropy, the stronger the password.
Entropy is calculated using the formula:
Entropy = L × log₂(N)
, where
L
is the password length and
N
is the size of the character set used.
📊 Example
16 × log₂(95) ≈ 105 bits — that's 2¹⁰⁵ possible combinations. A hacker would need billions of years to guess it.
How This Entropy Calculator Works
This tool analyzes your password in real-time as you type. It detects which character sets are used — lowercase, uppercase, digits, and symbols — and calculates the total character set size. It then applies the entropy formula to compute the strength in bits.
The calculator also shows you the live formula with your actual numbers filled in, a visual entropy scale showing where your password sits, a "what-if" table showing how adding characters or character types would change your entropy, and the combinations count expressed as a power of 2.
What Is a Good Entropy Score?
- < 40 bits: Very weak — can be cracked instantly. Avoid.
- 40–60 bits: Weak — vulnerable to basic attacks. Not recommended.
- 60–80 bits: Moderate — acceptable for low-risk accounts with 2FA.
- 80–100 bits: Strong — suitable for most accounts including email and social media.
- 100–128 bits: Very strong — recommended for banking, password managers, and critical accounts.
- 128+ bits: Extremely strong — effectively uncrackable with current technology.
How to Increase Your Password Entropy
The most effective way to increase entropy is to add more characters . Each additional character multiplies the total number of possible combinations by the size of your character set. Adding one character to a 95-character set password increases entropy by ~6.6 bits — doubling the search space 100 times.
Using a wider variety of character types also helps. A password with only lowercase letters has 26 possible characters per position. Adding uppercase, digits, and symbols expands this to 95 — a 3.6× increase per character, which compounds exponentially with length.