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Password Generator Strength Calculator

Work out password generator strength instantly with clear inputs, formula shown and shareable results.

About Password Generator Strength Calculator

Entropy is length times the base-two logarithm of the character set size, and the average crack time is half the search space divided by the guess rate. Each extra character adds a fixed number of bits, which is why length beats complexity: adding four characters helps more than adding symbols to a short password.

Formulas

Entropy

bits = length x log2(character set size)

Crack time

average seconds = 2^bits / 2 / guesses per second

Worked example

With the default values below, Password Generator Strength Calculator returns Entropy of 104.87. Change any input above and every figure here is recalculated in your browser.

Inputs used

Password lengthaccepts 1–128
16
Character set sizeaccepts 2–100,000
94
Attacker guesses per secondminimum 1
100,000,000,000

Results

Entropy
104.87 bits
Strength band
Very strong
Average years to crack at that rate
5,887,239,378,693.235000
Combinations as a power of ten
31.570

Step by step

  1. 1Values used
  2. 2Entropy
  3. 3Crack time
  4. 4Entropy= 104.87 bits
  5. 5Strength band= Very strong
  6. 6Average years to crack at that rate= 5,887,239,378,693.235000
  7. 7Combinations as a power of ten= 31.570

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 6 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Password Generator Strength figure worked out?

bits = length x log2(character set size). Entropy is length times the base-two logarithm of the character set size, and the average crack time is half the search space divided by the guess rate.

Why does this matter?

Each extra character adds a fixed number of bits, which is why length beats complexity: adding four characters helps more than adding symbols to a short password.

What do I need to enter?

Enter password length, character set size, attacker guesses per second. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.

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