MundoKit

Password entropy calculator

Enter how many random choices your generator makes and the size of its alphabet or word list. Get entropy in bits without entering a secret.

Inputs
Password length or number of words. Fixed separators add no entropy.
Example size only. Every character or word must be equally likely.

Results

Generation entropy
96 bits
Bits per choice
6
Possible sequences
≈ 7.9228 × 10^28
  • Assumes independent, uniformly random choices with replacement. Human selection, biased generators, forced character-class rules and word reuse constraints need a different model.
  • This does not estimate an entered password or a cracking time. No secret is requested.

Results update as you type. The share link stores your inputs after the # in the address, which is not sent to our server, but anyone you send it to can read them.

How it works

For independent, uniformly random choices with replacement, every sequence has the same probability. Shannon entropy simplifies to:

H = L × log₂(N); sequences = N^L

L is the number of characters or words and N is the number of equally likely choices at each position. Pool sizes are user assumptions, not certified generator settings. A fixed separator adds no entropy. Zero choices or a pool of one gives zero bits.

Bits are displayed to two decimals, bits per choice to four, and large sequence counts in approximate scientific notation. Intermediate entropy is not rounded. The local calculation accepts at most 100,000 choices and a positive safe-integer pool size.

NIST password guidance is about authentication systems; this tool does not assign a universal safe threshold. Human-chosen passwords, biased selections and generators that enforce character classes require other probability models. Choosing the words mode changes the interpretation, not the formula.

Worked examples

Random alphabet

16 independent choices from an example alphabet of 64 symbols give 16 × log₂(64) = 96 bits.

Random passphrase

Six independent words sampled with replacement from the EFF long list of 7,776 words give 6 × log₂(7,776) = 77.55 bits. Select the EFF preset for this example, or Custom random words to edit the count and pool size.

Frequently asked questions

Can I enter my password?
No. Entropy here describes the random generation process, not the appearance of a particular string.
Do uppercase letters automatically add entropy?
Only if they increase the number of equally likely random choices. Predictable capitalization does not count as a random choice.
Can I use this for Diceware?
Yes, if each word is chosen independently and uniformly with replacement. Select the EFF long-list preset for six words from 7,776, or Custom random words to enter your actual list size and word count.
Does this predict cracking time?
No. Guessing rate depends on hashing, hardware, online throttling and attacker strategy.
What if repeats are forbidden?
This formula does not apply. Sampling without replacement has a different sequence count.

Sources

Last reviewed 2026-11-14. The method is written out above so you can check our math.