Password Entropy Calculator
Measure a password's real strength in bits of entropy, without it ever leaving your browser.
An approximate estimate based on the alphabet size used and common predictable patterns — it's not a substitute for a real zxcvbn-style analysis with a full dictionary, but it gives a reliable sense of relative strength. Nothing is sent to any server, everything is calculated in your browser.
Built by
Miguel Ángel Colorado Marin (MACM)
Built by
Miguel Ángel Colorado Marin (MACM)
Full-Stack Developer · Guadalajara, España
I develop web apps, digital tools and full projects — from design to deployment.
This calculator measures a password's entropy (how many bits of real randomness it has) based on the symbol alphabet it uses and its length, and penalizes the result if it detects predictable patterns: very common words and sequences (password, 123456, qwerty...), keyboard or alphabetic sequences (abc, 123, qwe) and repeated characters in a row. It also estimates how long a brute-force attack at 10 billion attempts per second (a realistic figure for current dedicated hardware) would take to try every combination. Type a password and the analysis updates instantly — it never leaves your browser, there's no network connection involved.
Features
- ✓Real-time bits of entropy
- ✓Detection of common words and patterns
- ✓Detection of sequences (abc, 123) and repeats
- ✓Brute-force time estimate
- ✓100% in browser, the password is never sent
How to measure a password's strength?
- 1
Type the password
The analysis updates instantly as you type.
- 2
Check the bits of entropy
More bits = more possible combinations = harder to guess.
- 3
Fix the warnings if they appear
Common words, sequences or repeats lower the real security a lot.
Frequently asked questions
Is my password sent to any server?
No, never. All the analysis happens with JavaScript directly in your browser, there's no network request.
How many bits of entropy do I need?
Below 40 bits is considered weak, 60-80 is a good level for most accounts, and above 80 is very robust even against well-resourced attackers.
Is it as accurate as zxcvbn (Dropbox's analyzer)?
It doesn't try to be. zxcvbn uses massive dictionaries and elaborate substitution rules; this tool uses a simpler heuristic, useful as a quick reference but not a substitute for a real security audit.
Related tools
Embed Password Entropy Calculator on your site
Add Password Entropy Calculator to any web page with a simple iframe. Free, with attribution to miguelacm.es.
<iframe
src="https://miguelacm.es/embed/password-entropy"
width="100%"
height="700"
frameborder="0"
title="Password Entropy Calculator — miguelacm.es"
></iframe>