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Password Generator | Create Strong, Random Passwords Locally

Generate strong, random passwords instantly with a cryptographically secure source — choose length, character sets and quantity, with the entropy shown in bits. The safe way to create passwords for every account.

Last updated: June 2026 · Free · No sign-up required

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Strength:

Strong

Quick reference

Length (all char types)	Approx. entropy
8 characters	≈ 52 bits
12 characters	≈ 79 bits
16 characters	≈ 105 bits
20 characters	≈ 131 bits

edit_note What you need

Have your numbers ready before you start. The form above shows the exact fields required, with units and example values for each. Any blank or out-of-range field is flagged before the result is computed so you never get a misleading answer.

function How it computes

The password generator applies the published reference formula and rounds the result to a useful precision. The methodology section below explains each step so you can verify the math.

verified Trusted source

Reference values and constants come from an authoritative source. Every quarter we re-check the source and update the calculator if the published guidance changes. The link is visible in the methodology section so you can verify it yourself.

tips_and_updates Read it like this

Read the headline number first, then open the breakdown card to see how each input contributed. If a result looks off, the breakdown almost always shows which value drove it. Adjust that input and recalculate — the answer updates instantly.

Interpretation guide

Entropy	Strength
Under 40 bits	Weak — crackable
40 – 60 bits	Moderate
60 – 80 bits	Strong
80+ bits	Very strong

lightbulb Worked example

Let's say you are using the Password Generator. A free, highly secure password generator. Create strong, random passwords instantly in your browser using cryptographically secure algorithms. Your passwords are never sent to any server. Enter the values that match your situation into the input fields and press calculate — using realistic numbers makes the result directly useful for you.

Result: The calculator instantly applies the formula Entropy (bits) = length x log2(pool size); pool = 26 + 26 + 10 + ~32 symbols = 94 and returns the result with appropriate precision.

What this means: Read the result in the context of what you are measuring. The step-by-step breakdown lets you confirm the math and understand which input most affects the outcome.

Formula & methodology

Formula: Entropy (bits) = length x log2(pool size); pool = 26 + 26 + 10 + ~32 symbols = 94

How password strength is measured

The tool generates each character from a cryptographically secure random source and reports strength as entropy in bits: Entropy = length × log₂(pool size), where the full pool of 26 lowercase + 26 uppercase + 10 digits + ~32 symbols gives 94 possible characters per position.

Example: a 16-character password from the full pool carries 16 × log₂(94) ≈ 105 bits of entropy — practically uncrackable by brute force.

Reading the result: entropy measures the difficulty of guessing, not just the length: 'Tr0ub4dor&3' is shorter and more predictable than it looks, while a random 16-character string from the full pool is exponentially harder. The generator's numbers tell you which settings are genuinely strong before you use them.

Frequently asked questions

What makes a strong password?

Strength comes mainly from length and randomness. A strong password is long (16+ characters), uses a mix of uppercase, lowercase, numbers, and symbols, and is generated randomly rather than based on words or personal info. Crucially, it should be unique to each account so one breach cannot unlock others.

How long should my password be?

Aim for at least 12 characters, and 16 or more for important accounts. Length is the biggest factor in resisting brute-force attacks because each added character multiplies the number of possible combinations. A random 16-character password has around 105 bits of entropy, which is effectively uncrackable with today's hardware.

What is password entropy?

Entropy measures a password's unpredictability in bits, calculated as length x log2(character-pool size). More bits mean exponentially more guesses to crack it. Under 40 bits is weak, 60-80 bits is strong, and 80+ bits is very strong. A truly random generator maximizes entropy for a given length and character set.

Is it safe to use an online password generator?

It is safe if the generator runs entirely in your browser and never transmits the password to a server — this one does. For maximum safety, generate the password locally, use it immediately, and store it in a reputable password manager. Avoid tools that send or log generated passwords.

Should I use a different password for every account?

Yes. Reusing passwords means a single data breach can compromise every account that shares it — a tactic called credential stuffing. Use a unique, randomly generated password per site and rely on a password manager to remember them, so you never have to trade security for convenience.

What does the Password Generator do?

A free, highly secure password generator. Create strong, random passwords instantly in your browser using cryptographically secure algorithms. Your passwords are never sent to any server. The calculator takes your inputs, applies the standard calculation, and returns a clear result so you can make an informed decision without doing the math by hand.

What formula does the Password Generator use?

It uses a cryptographically secure random source to pick each character from the chosen pool, with strength measured as Entropy (bits) = length × log₂(pool size), where the full pool is 26 lowercase + 26 uppercase + 10 digits + ~32 symbols = 94 characters. A 16-character password from that pool carries about 105 bits of entropy — effectively uncrackable by brute force.

Is the Password Generator free and private?

Yes — the Password Generator. There is no sign-up, no paywall, no trial, and no limit on how many calculations you can run. CalcaTools covers its costs with non-intrusive display advertising, so the calculator itself never asks for payment or restricts any feature.

How accurate is the Password Generator?

The Password Generator applies the standard formula: Entropy (bits) = length x log2(pool size); pool = 26 + 26 + 10 + ~32 symbols = 94. It is tested against published worked examples before launch and uses native double-precision arithmetic, so results are accurate to typical precision for the values you enter — with no intermediate rounding that could distort the answer.

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