How this calculator works
Entropy depends on the generation process, not just the appearance of one password. For independent uniform draws, each position contributes the logarithm base two of its pool size. Fixed-pool mode assumes the positions of each character class are known; it does not add an arrangement bonus. A human-chosen word, reused password or predictable pattern can have much less uncertainty.
Formula
H = L log2(N) bits for one alphabet. For fixed independent positions from pools: H = sum(ni log2(Ni)). Search space = 2^H.
Worked example
Twelve independently random characters from 64 choices have 12 x 6 = 72 bits. Eight random decimal digits have about 26.5754 bits.
Advertisement
Frequently asked questions
Can this rate my existing password?
No. A single observed string does not reveal its generation distribution. Do not enter passwords into calculators.
What if I shuffle fixed character groups?
That can add uncertainty if the shuffle is random and unknown, but this conservative fixed-position model does not count it.
Does high entropy prevent phishing?
No. Entropy describes guessing uncertainty, not resistance to phishing, malware or password reuse.