Password Strength Calculator

Do not enter an actual password. Describe only its length and broad characteristics. This password strength calculator explains oc-password-heuristic-v1, an OverCalculator educational score; NIST does not define or endorse it, and a high result is not a security guarantee.

Entries and scoring rules

Enter an integer length from 1 to 128. The starting description is 14 characters with uppercase, lowercase, numbers, and special characters selected, and all four pattern flags off.

Length contributes 40 points at 16+, 30 at 12–15, 15 at 8–11, and 0 below 8. Each selected character class contributes 10 points. Common patterns subtract 20; repeated, sequential, and keyboard patterns each subtract 10.

The selected pools contain 26 lowercase, 26 uppercase, 10 numeric, and 33 special characters. Under a uniform-random assumption:

$\text{search-space bits}=\text{length}\times\log_2(\text{selected pool size})$

The score adds the smaller of 20 or the whole-number result of bits divided by 4, then is limited to 0–100. The crack-time label uses 2^bits/10^10 seconds as an offline toy scenario.

For the starting description, pool size is $26+26+10+33=95$ and the estimate is 14 log₂(95)≈92.0 bits. Length gives 30 points, the four classes give 40, and the capped search-space addition gives 20, for 90/100 and “Centuries or more.” A one-character description with all four classes selected gives 41/100 yet “Under one day,” illustrating why the score and toy time label answer different arithmetic questions.

Interpretation and action checklist

• Human-chosen text and known patterns violate the uniform-random model.
• Hash design, hardware, dictionaries, rate limits, and compromised-password data can radically change guessing outcomes.
• Do not use this score to certify a credential or compare two real secrets.
• Use a password manager where appropriate and check the service’s actual requirements.
• Follow verifier guidance on sufficient length and blocking common or compromised values rather than treating mandatory character mixtures as proof of strength.

To generate a uniformly random candidate string, see the random number generator; the leet-speak translator demonstrates the kind of character substitutions that human-chosen passwords commonly use and that the uniform-random model does not represent.

The next task is to create or store a credential through a trusted password manager or service workflow—not to paste it into this educational tool.

Source

• NIST, SP 800-63B-4 final (2025), section 3.1.1.2 — US federal password-verifier guidance; it does not define or endorse this calculator’s score.