The short answer
For any account that matters, use a random password of 16 characters or more with uppercase and lowercase letters, digits and symbols, and save it in a password manager. If you have to type or remember it, use a passphrase of 6 or more random words instead. Your password manager master password and your main email account deserve the longest ones, because they unlock everything else.
Current guidance from the US standards body NIST (SP 800-63B, revised in 2025) asks services to require at least 15 characters when a password is the only thing protecting an account, and to accept passwords of at least 64 characters. It also tells services to stop forcing regular password changes and stop demanding character mixes, and to block passwords that already appear in breach lists instead. In other words: length and uniqueness, not complicated rules.
Try it here: Password Generator
Open the full tool pageEntropy explained simply
Password strength is measured in bits of entropy. Each bit doubles the number of guesses an attacker needs. A random password has length times log2(pool size) bits, where the pool is the number of characters it could contain. Lowercase letters give about 4.7 bits per character, letters and digits about 5.95, and the full set of 87 characters used by the generator on this page about 6.44.
So a 16 character password from all four sets has about 103 bits, while an 8 character one has only about 51. Adding one character adds 6.44 bits, which multiplies the work by about 87. Adding a symbol to a short password helps far less than adding several characters.
Entropy only applies to passwords that are truly random. Summer2026! looks like it has 10 mixed characters, but attackers do not guess letter by letter: they try words, names, years and a capital at the start with a symbol at the end. Its real strength is a tiny fraction of what the formula suggests.
| Length | Lowercase only | Letters and digits | All 4 sets (87 chars) |
|---|---|---|---|
| 8 characters | 38 bits, about 10 seconds | 48 bits, about 3 hours | 51 bits, about 2 days |
| 12 characters | 56 bits, about 55 days | 71 bits, about 5,000 years | 77 bits, about 300,000 years |
| 16 characters | 75 bits, about 69,000 years | 95 bits, far beyond any lifetime | 103 bits, far beyond any lifetime |
| 20 characters | 94 bits, far beyond any lifetime | 119 bits, far beyond any lifetime | 129 bits, far beyond any lifetime |
What the cracking times mean
The times in the table are average times for an offline attack at ten billion guesses per second, the same assumption the generator above uses for its estimate. That speed is realistic for a few graphics cards attacking a leaked database that used a fast hash. Slow hashes such as bcrypt or Argon2 cut the speed by many orders of magnitude, while a large cloud cluster can raise it, so treat the times as a comparison, not a promise.
Online attacks against a login page are much slower because of rate limits, but you cannot know how a site stores passwords. Assume your password will one day leak as a hash, and pick one that survives that. Around 80 bits is very strong for any online account; 100 bits and more is a comfortable margin for a master password or encryption key.
Passphrases vs random strings
A passphrase is several words picked at random from a large list, for example with dice and the EFF or Diceware list of 7,776 words. Each word adds about 12.9 bits. Four words give about 52 bits, five about 65, six about 78 and seven about 90. Six random words are roughly as strong as a 12 character random password and much easier to type on a phone or a TV remote.
The words must be chosen at random, not by you. A line from a song, a quote or four words that form a sentence are all in attackers' dictionaries. Separators and capital letters add little; extra words add a lot.
Use a random string when the password lives in a password manager and you never type it. Use a passphrase for the few secrets you must remember: the password manager itself, your computer login and perhaps your main email.
| Method | Example length | Entropy | Best for |
|---|---|---|---|
| Random characters, all sets | 16 characters | about 103 bits | Accounts stored in a password manager |
| Random characters, all sets | 20 characters | about 129 bits | Wi-Fi keys, API secrets, encryption |
| Random words (7,776 word list) | 6 words | about 78 bits | Master password, device login |
| Random words (7,776 word list) | 7 words | about 90 bits | Password manager master password |
| Random digits | 6 digit PIN | about 20 bits | Phones and cards with attempt limits only |
Password managers do the hard part
Nobody can remember 100 unique 16 character passwords, which is why people reuse them, and reuse is how most accounts get taken over: one site leaks, and attackers try the same email and password everywhere else. A password manager stores a different random password for every site and fills it in for you, so the length costs you nothing.
Built in options are fine for most people: the managers in Chrome, Edge, Firefox and Safari, Apple Passwords on iPhone and Mac, and Google Password Manager on Android all sync across devices. Dedicated apps add sharing, emergency access and support for every browser. Protect the manager with a long passphrase and turn on two factor authentication for it and for your email.
PINs are a special case
A 4 digit PIN has only 10,000 combinations and a 6 digit PIN one million, which would be useless as a password. PINs work because the device enforces the limit: a phone erases itself or locks for hours after repeated wrong tries, and a bank card is blocked after three. That protection only exists on the device, so never reuse a PIN as a website password.
Avoid the PINs everybody picks: 1234, 0000, 1111, birth years and dates. Choose 6 digits when the device allows it, and let the PIN generator variant of this tool pick them for you.
What makes passwords weak
- Reuse: the same password on two sites means a leak at one opens both.
- Personal information: names, pets, birthdays, team names and places can be found on social media.
- Patterns: a capital first letter, a year and an exclamation mark at the end are the first variants tools try.
- Keyboard walks: qwerty, 1qaz2wsx and asdfgh are in every wordlist.
- Substitutions: P@ssw0rd and similar tricks are known and add almost nothing.
- Small changes: password1 to password2 after a forced reset is guessed immediately.
- Short length: under 12 characters, even a random password can fall to an offline attack.
Tips for using the generator
Leave all four character sets on unless a site rejects symbols; if it does, turn symbols off and add 2 or 3 characters to keep the same strength. Turn on Avoid look-alike characters for passwords you will read aloud or type from paper, such as a Wi-Fi key on a router label. This removes characters like 0 and O or 1, l and I and lowers the entropy slightly, so add a character or two.
Set How many to create a batch, for example temporary passwords for new staff accounts. The password is created with your browser's secure random generator and is never sent or stored, so copy it into your password manager before you leave the page.