Password generator: making passwords that are hard to guess
A strong password is the first line of defense for every online account, yet most people reuse a handful of weak ones. A password generator creates truly random strings from a configurable alphabet, lowercase, uppercase, digits, symbols, or a passphrase, at the length you choose. Because the entropy comes from the randomness of the source, generated passwords resist dictionary and brute-force attacks far better than human-chosen ones.
TL;DR
- The generator picks each character independently from the chosen character set using a random number generator.
- Entropy Formula: Entropy (bits) = Length × log2(Character Set Size) | Combinations = Set^(Length)
- Example 1: A 16-character full-set password — Character set: lowercase + uppercase + digits + symbols = 94 types
How it works
The generator picks each character independently from the chosen character set using a random number generator. The security of the result is measured in bits of entropy, which grows with the set size and the length: each additional character multiplies the number of possible combinations by the set size.
The math
For a character set of size S and a password of length L, the number of possible passwords is S raised to the power of L, and the entropy is L × log2(S) bits. Each bit doubles the work a brute-force attacker must do, so 80+ bits is a common security target.
A 12-character password using 94 symbol types yields 12 × log2(94) ≈ 78.6 bits of entropy; an 8-character lowercase-only password yields only about 37.6 bits.
Practical Password Strength Examples
Example 1: A 16-character full-set password
- Character set: lowercase + uppercase + digits + symbols = 94 types
- Entropy: 16 × log2(94) ≈ 104.8 bits
- Combinations: 94^16 ≈ 3.7 × 10^31
- Result: effectively unbreakable by brute force
Example 2: Why length beats complexity alone
- 8 chars, lowercase only: 26^8 ≈ 2.1 × 10^11 (37.6 bits)
- 8 chars, full set: 94^8 ≈ 6.1 × 10^15 (52.4 bits)
- 12 chars, lowercase only: 26^12 ≈ 9.5 × 10^16 (56.4 bits)
- Conclusion: longer lowercase passwords beat shorter complex ones
When to use it
✦ Account Sign-Ups and Resets
Users generate a unique strong password for every new account instead of recycling one weak password across services.
✦ Passphrase Creation
Systems that need memorable credentials generate random word sequences (Diceware-style passphrases) with high entropy and easier recall.
⚠ Common Password Security Mistakes
- Reusing Passwords: A leaked credential from one service unlocks every account that shares the same password.
- Using Dictionary Words: Human words and dates are the first targets of dictionary attacks; randomness removes that vulnerability.
- Storing Passwords in Plain Text: Even strong passwords are compromised if written on sticky notes or saved in unencrypted files, use a password manager.
Frequently Asked Questions About Password Generators (6)
How long should a password be?
For important accounts, 14-16 characters with a mix of character types is advisable; shorter passwords rely on complexity alone and are weaker.
What is a passphrase?
It is a sequence of random words joined by spaces or symbols, like "cobalt-sunset-chorus-42", offering high entropy while being easier to type.
Do you save the numbers I type for area, volume or conversions?
Not at all. Every conversion — kg to lbs, area, fraction math — runs locally. No form data is posted anywhere. You can convert 1,500 kg to lbs on a shared computer and walk away knowing nothing was logged.
Will it work without internet in class?
Yes — that's why students like it. Load once on Wi-Fi, then fraction, base-converter or standard deviation work offline in class or in an exam hall without signal. It's just math in JavaScript, no server round-trip.
How accurate are the math results?
We use standard definitions (e.g. 1 kg = 2.20462 lbs, BIPM SI) and double-check edge cases via automated tests. For homework or site measurements it's more than enough, but for certified engineering or lab work, cross-check with the primary standard.
Can I share a calculation with a classmate?
Tap 'Share Link' — it puts the inputs in the URL. Your classmate opens it and sees the same 3/4 → 0.75 → 75% breakdown instantly, without retyping.
Sources & References
How this calculator is maintained
This calculator is written and maintained by Davide Coronese, independent developer and founder of CalcTracker.
Methodology: every formula is checked against official publications and validated by an automated test suite before release. Health, tax and finance pages cite the exact sources they rely on.
Found an error? Contact us — verified corrections ship within 24 hours.