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Password Strength Checker

Check a password's strength based on its length and character variety.

Inputs

Password

Paste this into any page — the widget stays live and updates automatically as this calculator improves. Using WordPress or Notion? See the embed guide.

Saved Scenarios

— select 2+ to compare
Inputs updated · Results recalculated · Just now

Strength Score

0

Password Strength

Very Weak

Very WeakWeakFairStrongVery Strong

Rating

Empty

Spark says

Close-up of a smartphone wrapped in a chain with a padlock, symbolizing strong security.
Photo by Towfiqu barbhuiya on Pexels
Detailed close-up of a durable padlock securing a rusted metal gate, emphasizing safety and protection.
Photo by Damir K . on Pexels

Formula

Score=max⁡(0, min⁡(100, min⁡(Length×4,40)+Classes×15)−RunPenalty)Score = \max(0,\ \min(100,\ \min(Length \times 4, 40) + Classes \times 15) - RunPenalty)
Classes
— Count of character types used: lowercase, uppercase, digits, symbols
RunPenalty
— Deducts up to 40 points for adjacent characters that repeat or step by one (e.g. "aaaa" or "1234") — length alone doesn't earn credit for a predictable run

What is the Password Strength Checker?

This is a composition-based heuristic — it rewards both length and character variety (lowercase, uppercase, digits, symbols), which are the two factors most guidance agrees matter most for resisting guessing attacks. For a bits-of-entropy calculation instead, see the Password Entropy Calculator.

How to use it

  1. 1 Type a password to see its strength score and rating.

Worked examples

A long, mixed-character password

Scores 98/100 — "Very Strong" (20 characters, all 4 character types, no meaningful sequential runs).

Try it

A common sequential password

Scores 19/100 — "Very Weak". Ten characters and one character class alone would score "Fair", but the run penalty catches that it's one long ascending sequence, not 10 independent choices.

Try it

Limitations

  • •This runs entirely in your browser and is never sent anywhere — but it's still a heuristic score, not a guarantee: a long password made of a common phrase can score well here while still being easy to guess for an attacker with a dictionary of common phrases.

Frequently asked questions

Is my password sent to a server when I use this?

No — this calculator computes entirely client-side in your browser; the password never leaves your device or gets transmitted anywhere.

How is this different from the Password Entropy Calculator?

Entropy measures theoretical randomness in bits, useful for comparing generated passwords. This strength check is a simpler, composition-based heuristic closer to what many signup forms show you.

calixo.cloud/developer/password-strength-calculator/ — free calculator, no signup required.