Passphrase Generator
A password made of random common words, with the exact entropy stated so you can judge it rather than trust it.
Results
What this tool does
A string of random characters is strong and nobody remembers it, so it ends up written down or reused. A handful of random words is easier to hold in your head, easier to type on a phone and, given enough words, just as hard to guess. What matters is that the words are genuinely random and that you know how much that is worth: this page draws from a list of 512 words, so each one is worth exactly 9 bits, and the total is shown above rather than described as "strong".
Formula
entropy = number of words × log₂(list size) · a 512-word list = 9 bits per word
Variables
| Symbol | Meaning | Unit |
|---|---|---|
words | Words in the phrase | — |
separator | Between the words | — |
capitalise | Start each word with a capital | — |
add_number | Put a number on the end | — |
count | How many | — |
seed | Seed | — |
OUT | The passphrases | — |
EN | Entropy | bits |
LS | Words in the list | — |
BW | Bits each word is worth | bits |
CH | Characters | — |
Worked example
- Words in the phrase5
- Between the words-
- Start each word with a capitalno
- Put a number on the endyes
- How many3
- Seed11
- The passphraseslunch-media-paper-opera-such-58 black-media-paper-jacket-layer-85 hook-puppy-rabbit-clay-combine-34
- Entropy45.0 bits
- Words in the list512
- Bits each word is worth9.0 bits
- Characters31
Limitations
- The calculation runs entirely in your browser. The values you type are never sent to a server.
Frequently asked questions
How strong is 45 bits, really?
Five words from this list is 45 bits, which is about 35 trillion combinations. That is comfortable against someone guessing at a login form and thin against an attacker who has stolen the database and is testing offline at billions a second. The honest advice is to use more words: eight gives 72 bits, which is a different universe, and a passphrase of eight short words is still easier to remember than a random string of twelve characters.
Why only 512 words? Diceware uses 7776.
Because the whole site loads without fetching anything, and a list of 7776 words would be most of that budget for one page. The consequence is stated rather than hidden: this list gives 9 bits a word against the standard list's 12.9, so you need roughly three words here for every two there. The size of the list and the bits per word are both shown above, which means you can check the arithmetic rather than take my word for it — and if you want the standard list, generate the phrase with a tool that ships it.
Does the number at the end make it stronger?
Barely, and the entropy figure above deliberately does not count it. Two digits add under seven bits, and an attacker who knows the format — words joined by hyphens with two digits on the end — gains most of that back. It is there because many systems still insist on a digit, not because it improves the passphrase. Adding one more word would be worth more than the number.