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Simple Calculators

Password Generator

Create strong, random passwords in your browser — with a strength meter

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StrengthStrong · 103.09 bits
Options
16

Passwords are generated in your browser using the operating system's cryptographically secure random generator — nothing is sent anywhere or stored. Aim for 16+ characters with all four character types for a strong password, and use a unique one per site.

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Quick summary

Generate a strong, random password with the length and character types you choose — uppercase, lowercase, numbers, and symbols. The strength meter shows estimated entropy in bits: length × log2(pool size), so 16 characters drawn from all four types (87 characters) give about 103 bits. Passwords come from your device's cryptographically secure random generator and never leave your browser. Use a unique one for every account.

Reviewed by Simple Calculators TeamLast reviewed

How to use this calculator

  1. Drag the Length slider to the number of characters you want, from 4 to 64 (16 is the default).
  2. Turn the Uppercase (A–Z), Lowercase (a–z), Numbers (0–9), and Symbols (!@#…) switches on or off to match the site's password rules.
  3. Check the Strength meter, which shows a rating and the estimated entropy in bits for your settings.
  4. Press the Regenerate button for a fresh password with the same settings, as many times as you like.
  5. Press the Copy button and paste the password straight into your password manager or the sign-up form.

Password Strength Formula

Password Entropy

E=L×log⁡2NE = L \times \log_2 N
E
Estimated entropy in bits
L
Password length (characters)
N
Pool size: 26 uppercase + 26 lowercase + 10 numbers + 25 symbols, for the types you turn on

Worked example

16 characters with all four character types on

Given
L = 16
N = 26 + 26 + 10 + 25 = 87
Calculation
E=16×log⁡287≈16×6.443E = 16 \times \log_2 87 \approx 16 \times 6.443
Result
E ≈ 103.09 bits (Strong)

Frequently asked questions

Are these passwords safe to use?

Yes. Each password is generated in your browser using the Web Crypto API, the operating system's cryptographically secure random number generator, rather than a predictable pseudo-random function. Nothing is transmitted or logged. For the best protection, generate the password on your own device, copy it straight into a password manager, and use it for only one account.

What makes a password strong?

Length and true randomness matter most. Every extra character multiplies the number of possible passwords, so a long random password beats a short one with clever substitutions or dictionary words. With all four character types on, 16 characters give about 103 bits of entropy here. Avoid reusing passwords, and never base one on personal details like names or birthdays.

How is password strength calculated?

The meter estimates entropy as length × log2(pool size), where the pool is the total number of characters from the types you turned on. All four types give a pool of 87, so 16 characters score 16 × log2(87) ≈ 103.09 bits. Under 28 bits is rated Very Weak, under 36 Weak, under 60 Reasonable, under 128 Strong, and 128 or more Very Strong.

How long should my password be?

Use at least 16 characters when the site allows it. With all four character types, 12 characters give about 77 bits of entropy, 16 give about 103 bits, and 20 give about 129 bits, which this meter rates Very Strong. Longer is always better for a random password, especially since a password manager remembers it for you.

Will every password include each character type I turn on?

Not necessarily. Each character is drawn at random from the combined pool of every type you enabled, so a short password may happen to contain no digit or no symbol. If a site insists on at least one of each, check the result and press Regenerate until it qualifies — longer passwords almost always include every type.

Is the password stored or sent anywhere?

No. The password is created in your browser and exists only on your screen until you copy it — it isn't sent to a server or saved by the site. Only your option settings, such as length and character types, are remembered for this browser tab. Once you leave the page the password is gone, so copy it first.

Should I use a different password for each site?

Yes. If you reuse a password, one breached site can expose every account that shares it. Generate a unique random password for each account and keep them in a reputable password manager, which fills them in for you so you don't have to remember them. Turn on two-factor authentication wherever it's offered for extra protection.

Key terms

Entropy
A measure of password randomness in bits; higher is harder to guess.
Web Crypto API
The browser's cryptographically secure random source used here.
Password Manager
An app that stores unique passwords so you needn't memorize them.

Methodology, sources & limitations

This page shows the formula, assumptions, and limitations used for this estimate. Rates, thresholds, and other time-sensitive inputs can change, so verify them against the relevant official source before relying on a result.

For our review approach and the primary sources we consult, see the methodology and source policy. If you spot an outdated figure or formula, please contact us with a correction.