Password Generator & Strength Checker
Generate a random password and instantly see how strong it is in bits of entropy.
chars
Character classes
Higher entropy means a harder-to-guess password.
- 1
Character pool
89Total symbols available from selected character classes. - 2
log₂(pool)
log₂(89) = 6.4757 - 3
Entropy (bits)
16 × 6.4757 = 103.6
How does this calculator work?
A password generator builds a random string from your chosen character classes and rates its strength using entropy E = L × log2(R) in bits, where L is length and R is the pool size. Longer passwords with more character types yield higher entropy and dramatically longer crack times.
Formula
How this is calculated
You pick a password length L and a set of character classes. Each class adds characters to the pool: lowercase letters contribute 26, uppercase 26, digits 10, and symbols about 32. The total pool size R is the sum of the selected classes. A password is built by drawing L characters uniformly at random from that pool.
Strength is measured as Shannon entropy, E = L × log2(R), expressed in bits. Each extra character adds log2(R) bits, so longer passwords and larger pools both increase entropy. The strength percentage compares E to a 128-bit reference (a common "very strong" target): Strength% = min(100, E / 128 × 100).
Crack time assumes an attacker guessing the full keyspace at 10 billion guesses per second, needing about half the 2^E combinations on average, so time ≈ 2^E / 2 / 1e10 seconds. This is a rough estimate: real attackers may be faster or slower, and reused or dictionary-based passwords fall far short of their theoretical entropy. The built-in generator uses Math.random, which is fine for casual use but not cryptographically secure for high-value secrets.
Frequently asked questions
Entropy is the number of bits needed to describe how unpredictable a password is. It equals length times log2 of the character pool size. More bits means exponentially more guesses are required to crack it.
Around 60 bits is reasonable for most accounts, 80+ bits is strong, and 128 bits is considered very strong and effectively uncrackable by brute force with current technology.
It uses Math.random for convenience, which is suitable for casual passwords but not for cryptographic keys. For high-value secrets, use a reputable password manager that relies on a secure random source.
Also known as
TG we-Calculate Editorial Team. (2026). Password Generator & Strength Checker [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/password-generator
TG we-Calculate Editorial Team. "Password Generator & Strength Checker." TG we-Calculate. 2026. https://we-calculate.com/calculator/password-generator.
TG we-Calculate Editorial Team, "Password Generator & Strength Checker," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/password-generator
@misc{wecalculate_password_generator, title = {Password Generator & Strength Checker}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/password-generator}}, year = {2026}, note = {TG we-Calculate} }
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