Password Entropy Calculator
Instantly measure the true strength of your password in "bits."
🔍 Advanced Entropy Analyzer
Strength Score
-- / 100Entropy (bits)
--Guesses Needed
--Estimated Crack Time
--What is Password Entropy?
Password entropy, measured in **bits**, is the most accurate, mathematical way to measure a password's strength. It represents how unpredictable and random your password is. The higher the entropy, the more secure your password.
Think of it this way:
- A 4-digit PIN (like '1234') has very low entropy. There are only 10,000 possible combinations.
- A random 12-character password (like
k!9W@sP4z&Lq) has astronomically high entropy, with trillions of combinations.
Each "bit" of entropy **doubles** the password's strength. This is why a small increase in a password's entropy makes it exponentially harder for a hacker to guess.
How This Calculator Works (The Modern Way)
This is not a simple character-counting tool. Old, simple calculators would see a password like P@ssword1! and give it a high score because it has uppercase, lowercase, numbers, and symbols. This is dangerously misleading.
Our advanced calculator uses a pattern-matching algorithm (inspired by `zxcvbn`) to find the "weakest link" in your password. It checks your password against vast dictionaries of:
- Common passwords (like 'password', '123456')
- Dictionary words (like 'sunshine', 'family')
- Simple substitutions ('@' for 'a', '!' for 'i')
- Keyboard patterns ('qwerty', 'asdf')
- Dates and repeating characters ('1990', 'aaa')
The entropy score you see is based on the *easiest possible way* a hacker could guess your password. This gives you a true, real-world measure of its security. For a deep dive into the concept, the Wikipedia article on computational entropy is a great resource.
What's a "Good" Entropy Score?
Here is a simple breakdown of what the entropy (bits) score means for your password's security against an offline attack:
< 40 bits
VERY WEAK. Can be cracked in seconds to hours. These are typically simple patterns, common words, or short passwords.
< 40-60 bits
MODERATE. Can be cracked in days to months. This is not secure enough for any important account. Our tool will show this as 'Fair'.
< 60-80 bits
STRONG. Can take years to centuries to crack. This is a good target for most of your online accounts.
< 80+ bits
VERY STRONG. Computationally infeasible to crack. This is 'fortress-level' security, ideal for email, banking, and password managers.
As recommended by the National Institute of Standards and Technology (NIST), the best way to achieve high entropy is to use a long password. For example, a random 16-character password from our Strong Password Generator will almost always have an entropy score over 100 bits.
Frequently Asked Questions
What is a good entropy score for a password?
A 'bit' of entropy doubles the password's strength.
- < 40 bits: Very Weak (crackable in seconds to hours)
- 40-60 bits: Moderate (crackable in days to months)
- 60-80 bits: Strong (crackable in years to centuries)
- 80+ bits: Very Strong (computationally infeasible to crack)
Why is 'P@ssword1!' a low-entropy password?
Because it's not random. It's a common dictionary word ('password') with a common substitution ('@' for 'a') and a common number pattern ('1') at the end. Our advanced calculator detects these patterns, just like a hacker's software would, and assigns the low entropy score it deserves. You can learn more in our guide to weak passwords.
Does this tool save my password?
Absolutely not. This tool is 100% client-side, meaning all calculations happen in your browser. No password data is ever sent to our servers, logged, or stored. Your security is our top priority.