Calculating your entropy is straightforward once you know the Password Entropy formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Password Entropy Calculator.
What is Password Entropy?
The Password Entropy calculation tells you your entropy from a few simple inputs. The figure you are solving for here is the entropy.
The Password Entropy formula
This calculation combines several inputs through a multi-step method rather than a single one-line formula. Enter the values below and the calculator resolves each step in order. The inputs it needs are:
- Password length — a number. Example: 12.
- Character set size — a number. Example: 94.
How to calculate it step by step
- Write down the password length (for example, 12).
- Write down the character set size (for example, 94).
- Apply the formula above to get your entropy.
- Double-check the result with the Password Entropy Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Password length | 12 |
| Character set size | 94 |
| Entropy | 78.7 |
| Possible combinations (log10) | 23.7 |
With password length of 12 and character set size of 94, the entropy works out to 78.7.
Example 2
With password length of 24 and character set size of 94, the entropy works out to 157.3.
| Result | Value |
|---|---|
| Entropy | 157.3 |
| Possible combinations (log10) | 47.4 |
Example 3
With password length of 6 and character set size of 94, the entropy works out to 39.3.
| Result | Value |
|---|---|
| Entropy | 39.3 |
| Possible combinations (log10) | 11.8 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Password Entropy Calculator does it instantly, for free, with the formula and a worked example built in.
Related calculators
Continue exploring utility calculators with these tools: Bleach Dilution Calculator, Pool Chlorine Calculator, Age Calculator, Percentage Calculator, Date Difference Calculator.