Password entropy measures how unpredictable your password is — higher entropy means stronger resistance to brute-force attacks. Enter any password below to calculate its entropy bits, estimated crack time, and actionable security insights.
Entropy (measured in bits) represents the number of guesses required to crack your password. Each additional bit doubles the difficulty. The formula is:
Entropy = Length × log₂(Character Set Size)
For example: A 12-character password with lowercase letters (26 possibilities) has ~56 bits of entropy. Add uppercase letters, digits, and special characters (95 possibilities), and the same length gives ~79 bits — 8 million times stronger!
Recommendation: Aim for ≥60 bits for standard accounts, ≥80 bits for email and social media, and ≥100 bits for banking, password managers, and sensitive data. Your password's resistance grows exponentially with each additional bit of entropy!
Password entropy is a mathematical measure of password strength, calculated as E = L × log₂(C) where L is length and C is character set size. Higher entropy means exponentially more guesses needed to crack your password via brute force. For example, a 64-bit entropy password requires up to 18.4 quintillion guesses, making it impractical for attackers to crack.
Security experts recommend: 60+ bits for basic online accounts (low risk), 80+ bits for sensitive accounts like email or social media, and 100+ bits for financial services, password managers, or any high-value data. Entropy above 128 bits is virtually uncrackable with current technology, even with nation-state resources.
Our calculator examines four character types: lowercase letters (26), uppercase letters (26), digits (10), and special symbols (~33). It counts which types are present to determine your character set size. Then it multiplies your password's length by log₂(character set size). All calculations happen locally in your browser — your password never leaves your device, ensuring complete privacy.
A larger character set dramatically increases entropy: lowercase only = 26 possibilities, lowercase+uppercase = 52, +digits = 62, +special chars = 95+. For maximum security, use at least 12 characters combining all four types. Example: "Tr0ub4dor&3" uses 95-character set, giving ~79 bits of entropy for 12 characters.
Yes. A short password with mixed characters can equal the entropy of a longer lowercase-only password. Example: "P@55w0rd" (8 chars, ~75-character set) ≈ 47 bits entropy, while "correcthorsebatterystaple" (25 chars, 26-character set) ≈ 117 bits entropy. Length often provides the biggest impact when combined with complexity.
Our crack time estimate assumes an offline attacker with high-end hardware capable of 1 billion (1e9) guesses per second — typical for modern GPU-based cracking rigs. For online attacks (website login forms), rates are much slower (hundreds per minute), making even moderate entropy passwords safe. However, always assume passwords could be stolen via data breaches, where offline cracking applies.
Absolutely not. All entropy calculations are performed locally in your browser using JavaScript. Your password never leaves your device, is not stored, logged, or transmitted over any network. We respect your privacy and security completely — this is why you can safely test any password, including your real ones.