Sixteen characters picked at random from the default set of 76 add up to 99.97 bits, rounded to 100, or 99.7 bits when one of each type is required. That meets the US Cybersecurity and Infrastructure Security Agency's public advice of at least 16 characters. Four high-end GPUs hammering a leaked NTLM hash would still need about 17 billion years to get through half the possibilities.
The length the public is told to use
When CISA, the US government's cybersecurity agency, explains passwords to the general public, it does not quote a standard. It gives three rules: make passwords long, make them random, make them unique. "Long" means at least 16 characters, and "random" means a string of mixed-case letters, numbers and symbols, or alternatively a memorable string of four to seven unrelated words. CISA also recommends a password manager to generate and store them, so that the only one you must remember is the manager's own.
Sixteen is a round, generous number. It clears the 15 characters NIST now demands of a password used alone, with one to spare, fits inside every common maximum length, and is short enough that the occasional manual entry is not a chore.
Generate a 16-character password
- Leave the length at 16 and all four character types on.
- Turn on look-alike exclusion only if you expect to read or type it by hand.
- Press Generate; the meter should read just under 100 bits.
- Put it in your password manager before pasting it anywhere else.
- Repeat for every account, so no two sites share a password.
How 16 random characters compare with common defaults
Many tools you already use produce passwords of their own. Their strength depends on both the length and the character set, so here they are side by side, with this page's 16 characters at the bottom. The bit figures for Apple and Windows LAPS are the ones those vendors publish.
Average time to search half the space, assuming an offline attack on a stolen fast hash:
| Password type | Bits | 10¹² guesses per second | 10¹⁴ guesses per second |
|---|---|---|---|
| Four random EFF words | 51.7 | 30 minutes | 18 seconds |
| Apple's 20-character strong password | 71 | 37 years | 137 days |
| Six random EFF words | 77.5 | 3,505 years | 35 years |
| Chrome's 15-character default | 87.0 | 2 million years | 24 thousand years |
| Windows LAPS 14-character default | 89.0 | 10 million years | 98 thousand years |
| This page, 16 letters and digits | 95.2 | 711 million years | 7 million years |
| This page, 16 of all four types | 99.7 | 17 billion years | 168 million years |
The two rates are assumptions, labelled by guesses per second. 10¹² is roughly four RTX 4090 cards attacking NTLM (one card ran about 288 billion NTLM guesses per second in a published hashcat benchmark). 10¹⁴ is a hypothetical attacker a hundred times bigger. Against a slow, salted hash such as bcrypt or Argon2, all rates fall by many orders of magnitude, and an online attacker is held to a small number of attempts by lockouts.
The table shows something useful: everything from Chrome's default downward is already out of reach for random passwords. Sixteen characters is not about surviving a cleverer attacker than 15 characters would; it is a margin that costs nothing when software fills it in.
Sixteen characters with other settings
Turning options off at this length still leaves plenty. With the every-type rule active, the figures are:
| Settings at 16 characters | Bits shown |
|---|---|
| All four types (default) | 99.7 |
| All four, look-alikes excluded | 97.8 |
| Letters and digits | 95.2 |
| Lowercase and digits | 82.7 |
| Lowercase only | 75.2 |
Even the lowercase-only version beats a typical eight-character password with every symbol by about 25 bits. If a site accepts 16 characters but limits which kinds, use whatever it allows and keep the length.
Where 16 characters fit
- Website and app accounts saved in a password manager. This is the default most people should use.
- Email accounts, which are the reset route for everything else and deserve the extra margin.
- Shared accounts in a team vault, where nobody types the password by hand.
- Router and network equipment admin pages, which are sometimes reachable from more places than you expect.
Where something else works better
- Typing on a television or console. Symbols and mixed case are painful with an on-screen keyboard; the Wi-Fi preset is built for that.
- Passwords you must memorize. A passphrase is easier to learn than 16 random characters.
- Sites that reject symbols. The no-symbols preset keeps 16 characters and drops to about 95 bits.
- Phones and PIN pads. Use the PIN preset where only digits are possible.
What 100 bits does not cover
Entropy measures resistance to guessing. It cannot stop a fake login page from collecting the password, malware from reading it as you type, or a service from storing it carelessly. Unique passwords limit the damage of any one leak, and a second factor or passkey protects the account even if the password escapes.
Your password and this page
The generator runs locally in your browser. The 16 characters are never transmitted, saved, or logged by the page, and they disappear from memory when you reload or leave.
Behind the generator
Characters are selected with crypto.getRandomValues. A remainder-based mapping would slightly favor some characters, so the generator uses rejection sampling and redraws biased values. The "one of each" count includes only the 85.7% of 16-character strings that contain every type, which is why the meter shows 99.7 rather than 99.97 bits. To confirm the page sends nothing, follow the steps on the methodology page.
FAQ
Why 16 characters and not 15?
Fifteen meets the NIST minimum for a password used alone; sixteen matches CISA's public advice and leaves one character of margin. Either is far beyond guessing attacks when generated randomly.
Is 100 bits overkill?
For a guessing attack, more than enough. The extra length is free when a password manager fills it in, and it protects you if a site uses a fast hash.
Can I memorize a 16-character random password?
Some people do, but most find it hard. If you need to remember it, use a six-word passphrase instead, which is easier to recall at roughly 77.5 bits.
Does a 16-character password need symbols?
No. Sixteen letters and digits give about 95 bits. Leave symbols on unless a site rejects them, because they cost nothing when software does the typing.
Will every site accept 16 characters?
Most will, since NIST asks services to accept at least 64 characters. If a site truncates or rejects it, lower the length until it is accepted, and sign in once more to make sure the whole password was saved.
Sources
- CISA Secure Our World: Use strong passwords
- Apple Platform Security: Automatic strong passwords
- Microsoft Learn: Windows LAPS entropy table
- Chromium password generator source
- NIST SP 800-63B-4
- Hashcat v6.2.6 on RTX 4090
Checked 2026-10-11.
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