Skip to content
Allin
Sign up · Sign in

Password entropy calculator

Measure a password's real strength, or the entropy of a randomly generated one.

Related tools

All Hashing & crypto tools →
Adler32 Checksum CalculatorGenerate a Adler-32 hash of any text instantly in your browser, with hex or Base64 output. Used in zlib and PNG.CRC32 Checksum CalculatorGenerate a CRC32 hash of any text instantly in your browser, with hex or Base64 output. Fast integrity check (zip, PNG).CRC64 Checksum CalculatorGenerate a CRC64 hash of any text instantly in your browser, with hex or Base64 output. ECMA-182, 64-bit integrity check.CSS Box Shadow GeneratorDial in a CSS box-shadow with live preview and copy the generated code — offset, blur, spread, color, inset.FNV-1a Hash GeneratorGenerate a FNV-1a hash of any text instantly in your browser, with hex or Base64 output. Fast non-cryptographic 64-bit hash.JWT GeneratorBuild and HMAC-sign a JSON Web Token in your browser — HS256, HS384 or HS512.MD5 Hash GeneratorGenerate a MD5 hash of any text instantly in your browser, with hex or Base64 output. 128-bit digest — fast, but not for security.MurmurHash3 GeneratorGenerate a MurmurHash3 hash of any text instantly in your browser, with hex or Base64 output. Fast 32-bit hash for hash tables.

The Password entropy calculator turns Length of a random password, Character set into Entropy (bits), Strength, instantly and for free. For instance, with Length of a random password = 12 and Character set = Lowercase (26) it returns Entropy (bits) = 56.405 and Strength = fair.

How to use it

  1. Enter your values: Length of a random password, Character set.
  2. Read the result instantly: Entropy (bits), Strength.

Frequently asked questions

How does the Password entropy calculator work?

It takes Length of a random password and Character set and derives Entropy (bits) and Strength from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

2 values: Length of a random password and Character set. Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Length of a random password = 12 and Character set = Lowercase (26), the calculator returns Entropy (bits) = 56.405 and Strength = fair. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Length of a random password = 24 and Character set = Upper + lower (52) instead, Entropy (bits) goes from 56.405 to 136.811 — which is why it is worth testing a few scenarios rather than trusting a single figure.

Which “Character set” option should I choose?

You can pick between « Lowercase (26) », « Upper + lower (52) », « Letters + digits (62) » and « + symbols (95) ». Each one changes what the calculator works out, so switch and compare — the default is « Lowercase (26) ».

What does it give for smaller values?

Scaled down to Length of a random password = 6 and Character set = Lowercase (26), Entropy (bits) comes out at 28.203. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Verifying a download matches its published checksum, comparing two files without reading them, and generating a signature for an API request.

What is the most common mistake?

Hashing a password with a fast algorithm. MD5 and SHA are built to be quick, which is exactly wrong for passwords — those need a deliberately slow function like bcrypt, scrypt or Argon2.

Where do the figures come from, and how current are they?

The digests follow their published specifications and are computed by the browser's own crypto implementation where one exists, so a value can be checked against any other conforming tool.

Further reading

All guides →
ExplainerPassword Entropy: What a Strength Meter Cannot KnowEntropy measures the process that produced a password, not the characters in it. H = L x log2(R) is only true when every character was chosen at random — which is exactly why a meter scoring a human-invented password on its character classes is measuring the wrong thing.GuideWhat a Password Manager Cannot MeasureEntropy prices one attack: offline guessing against a stolen hash. Above roughly 90 bits the number stops deciding anything — and the meter on this site under-reported a random 20-character password in 300 draws out of 300.ExplainerPassword Entropy Explained: Bits, Length, and How Long a Password Takes to CrackWhat password entropy really measures, why length beats complexity, and how bits of entropy translate into a realistic crack time.ExplainerBig O Notation for Beginners: O(1), O(n), O(n squared), and O(log n) ExplainedBig O describes how an algorithm's work grows as input grows. Here is what O(1), O(n), O(n squared), and O(log n) mean and why the difference matters.ExplainerWhat Is UTF-8 and Unicode? Code Points, Byte Encoding, and Why UTF-8 WonUnicode assigns every character a code point; UTF-8 encodes those code points in one to four bytes. Here is how it works and why it beat the alternatives.GuideSecuring a Home Wi-Fi Network: the Key, the Protocol and the Guest NetworkThe generator's random source audited line by line, what SAE actually removes, why transition mode gives most of it back, and the thing every guest-network guide leaves out.