OmniCalc

Password Generator

Random & Fun

Generate secure random passwords

Weak, reused, and predictable passwords are one of the leading causes of account breaches. Our password generator creates strong, truly random passwords in an instant — no need to invent one yourself or reuse an old favorite. Set your desired length and choose which character types to include (uppercase letters, lowercase letters, numbers, and symbols), and the tool generates a password that's statistically very hard to guess or crack.

Unlike passwords humans invent — which tend to lean on real words, birthdates, or predictable substitutions like '@' for 'a' — a properly generated random password draws each character independently and uniformly from your selected character set, giving it maximum entropy for its length. That randomness is exactly what makes it resistant to both guessing and brute-force attacks.

For best security, pair a strong generated password with a password manager so you never have to memorize it, and use a unique password for every account.

Why Password Generator Matters

Passwords remain the primary line of defense for almost every online account, and attackers exploit weak ones constantly through credential stuffing (trying leaked username/password pairs across many sites), dictionary attacks (trying common words and patterns), and brute-force attacks (systematically trying every combination). A long, random, unique password dramatically raises the cost of all three attack types, often making them practically infeasible with current computing power.

Beyond individual account security, strong random passwords matter anywhere a shared or default credential creates risk: securing a new Wi-Fi router, setting up a database or server account, generating an API key placeholder, or protecting a shared document. Security guidance from organizations like NIST now emphasizes password length and uniqueness over forced complexity rules and frequent changes, because long random passwords generated by a tool like this are both stronger and, when paired with a password manager, no harder to actually use than a weak one.

The Password Generator Formula, Explained

Entropy (bits) = log2(character set size ^ password length) = length × log2(character set size)

Password strength is measured in bits of entropy, which represents how many possible passwords could exist given your character set and length — a higher number means exponentially more possible combinations for an attacker to search through. The character set size depends on which types you include: lowercase letters (26), uppercase letters (26), digits (10), and symbols (commonly around 32), for a maximum full set of about 94 characters.

Each additional character you add to the length multiplies the total number of possible passwords by the character set size, which is why length matters more than almost anything else: a 16-character password from a 94-character set has about 2^105 possible combinations, versus about 2^79 for a 12-character password from the same set — a difference of over 33 million times more possible combinations for just 4 extra characters.

As a practical benchmark, security guidance generally treats 60+ bits of entropy as strong for typical online accounts, and 80+ bits as very strong. An 8-character password using only lowercase letters (26-character set) has roughly 37.6 bits of entropy and could theoretically be brute-forced in about 10 seconds at 10 billion guesses per second, while a 12-character password mixing all four character types (94-character set) has about 78.7 bits — which would take an estimated hundreds of thousands of years to brute-force at the same guessing rate.

How to Use the Password Generator: Step by Step

  1. Set the password length

    Choose how many characters the password should have. 12–16 characters is a reasonable minimum for most accounts; use 20+ for highly sensitive accounts.

  2. Select character types

    Check which character sets to include: uppercase letters, lowercase letters, numbers, and symbols. Including all four maximizes entropy for a given length.

  3. Click generate

    The tool instantly produces a random password drawing uniformly from your selected character sets.

  4. Copy and store it securely

    Copy the generated password directly into a password manager rather than memorizing or writing it down, and use a unique password for each account.

Password Generator Examples: Real-World Scenarios

1

Strong Password for a Banking Account

A user wants a maximally strong password for a financial account, using all four character types at a generous length.

Length:16
Character set:Upper + lower + digits + symbols (94)

Calculation

Entropy = 16 × log2(94) ≈ 16 × 6.554 ≈ 104.9 bits

Result

About 104.9 bits of entropy — far beyond the 80-bit 'very strong' benchmark, making brute-force attacks computationally infeasible with current technology.

2

Standard Password for a General Account

A user generates a typical 12-character password with all character types for a everyday online account, a common default length.

Length:12
Character set:Upper + lower + digits + symbols (94)

Calculation

Entropy = 12 × log2(94) ≈ 12 × 6.554 ≈ 78.7 bits

Result

About 78.7 bits of entropy, solidly in the 'strong' range and estimated to take on the order of hundreds of thousands of years to brute-force at 10 billion guesses per second.

3

Why Short, Simple Passwords Fail

A user creates an 8-character password using only lowercase letters, a common but weak pattern (e.g., a plain dictionary word).

Length:8
Character set:Lowercase only (26)

Calculation

Entropy = 8 × log2(26) ≈ 8 × 4.700 ≈ 37.6 bits

Result

Only about 37.6 bits of entropy — a modern system could brute-force every possible combination in roughly 10 seconds at 10 billion guesses per second, illustrating why length and character variety both matter.

Common Mistakes to Avoid

  • Reusing the same password across multiple accounts — if one site is breached, attackers immediately try the same credentials on other popular sites (credential stuffing), so a single reused password can compromise many accounts at once.
  • Prioritizing 'complexity tricks' like swapping 'a' for '@' over length — these substitutions are well-known to attackers and add far less entropy than simply making the password longer.
  • Storing generated passwords in an unencrypted text file, note app, or sticky note instead of a dedicated password manager, which undermines the security benefit of generating a strong password in the first place.

Tips & Tricks

  • Use a password manager to generate, store, and auto-fill unique strong passwords for every account, so you never need to remember or reuse one.
  • When a site limits length or disallows symbols, use the maximum length and character variety it allows — even a shorter random password from this tool beats a self-invented one, since it avoids predictable patterns entirely.

A strong password isn't about being clever — it's about being long, random, and unique. This generator handles all three automatically, giving you a password that's dramatically harder to crack than anything typed from memory. Store it in a password manager, use a fresh one for every account, and pair this tool with our Random Number Generator whenever you need a random PIN or code.

Password Generator — Frequently Asked Questions

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Authoritative References

NIST SP 800-63B — Digital Identity Guidelines (Authentication)

nist.gov — Official federal guidance on password length, complexity, and best practices

CISA — Creating and Managing Strong Passwords

cisa.gov — U.S. government cybersecurity guidance on password strength and password managers

External links open in a new tab. OmniCalc.us is not affiliated with these organisations.

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