Entropy analyzer
Estimate password entropy from length and character variety.
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Tool guide
Entropy analyzer: how it works
Practical information to understand the result and use this tool correctly.
About Entropy analyzer
Pool bits are an upper bound: character length times log2 of the detected alphabet (lowercase 26, uppercase 26, digits 10, symbols 33, space 1).
Shannon bits measure the actual character variety of the typed password, so repeated characters lower the score.
Bands: below 28 bits is low, below 50 is fair, below 70 is strong, and 70 or more is very strong.
A dictionary phrase like correcthorsebatterystaple can be weaker than its pool bits suggest.
How to use it
- 1Type the password; it is never uploaded.
- 2Read pool bits, Shannon bits, alphabet size, and the strength band.
- 3Toggle hide/show and copy the summary if you need it.
Frequently asked questions
- How is password entropy calculated?
- Pool bits = length x log2(alphabet size). A 12-character password using lowercase, uppercase, and digits has an alphabet of 62, so 12 x log2(62) is about 71.4 bits.
- What is the difference between pool bits and Shannon bits?
- Pool bits assume every position is a uniform random pick over the alphabet. Shannon bits also account for repeated characters, so a password with many repeats scores lower.
- How many bits should a password have?
- Bands used here: under 28 bits is low, under 50 is fair, under 70 is strong, and 70 or more is very strong.
- Is my password sent anywhere?
- No. The estimate runs entirely in your browser and the field is never uploaded.