How Strong Is Your Password Really?

Entropy is length times bits per character

A character drawn at random from the 95 printable symbols carries about 6.57 bits. One drawn from the 26 lowercase letters carries 4.70. Multiply by length and you have the total.

Twelve characters from the full symbol set is 78.8 bits.

Start with the catch, because it's the whole story

That figure assumes every character was picked independently and uniformly at random.

A password a person invented is nothing like that. It's built from words, names, dates, keyboard runs and predictable substitutions — and a cracker tries exactly those patterns first, long before working through the space one combination at a time.

P@ssw0rd123! is twelve characters using all four character classes. This tool scores it at 78.8 bits. Its real strength against a modern wordlist with substitution rules is a tiny fraction of that.

The number is an upper bound. It equals real strength only when a machine did the choosing.

Length beats complexity, and here's the size of it

Every extra character adds the same number of bits. Changing the alphabet only changes how much each one adds — and that change is small.

Alphabet	Bits per character
Digits (10)	3.32
Lowercase (26)	4.70
Letters + digits (62)	5.95
Letters, digits, symbols (95)	6.57

Going from 62 characters to 95 buys you 0.62 bits per character. Across an eight-character password that's under five bits total.

Adding four more characters at the smaller alphabet adds nearly twenty-four.

That's the whole argument for passphrases in one comparison, and it's why "add a symbol and a number" was always the weaker half of the standard advice.

The attacker's speed matters more than your password

This is the part that surprises people. Same twelve-character password, 78.8 bits:

What the attacker can try	Average time to crack
100/sec — rate-limited login	86 trillion years
100 billion/sec — stolen hash, GPU rig	86,000 years

Nine orders of magnitude apart, from one assumption about how the guessing happens. Across the full range in the tool it's about twelve.

That dwarfs any realistic difference in password choice — which is why the attack rate is a dropdown rather than a hidden constant. Picking a row is choosing which threat you're reasoning about, and pretending there's one right number would hide that.

What actually falls quickly

At a GPU-rig rate against a fast hash:

Password	Bits	Time
6 lowercase	28.2	instant
8 letters + digits	47.6	18 minutes
8 with symbols	52.6	9 hours
12 lowercase	56.4	5.5 days
12 with symbols	78.8	86,000 years

Note the third and fourth rows. Twelve lowercase letters beats eight with symbols — a longer, easier-to-type password outperforming a shorter cryptic one, exactly as the bits-per-character table predicts.

Reading the powers-of-ten output

Once a crack time passes a few billion years the exact figure stops meaning anything, so the tool reports the exponent as well.

A jump from 10 to 16 there is six orders of magnitude — a million times harder. Far clearer than two enormous numbers side by side.

It also stays useful at the weak end, where it goes negative: −3 means the password falls in about a thousandth of a second.

How many bits to aim for

80 is a reasonable floor for an ordinary account. 128 is the target for anything long-lived — a manager's master password, a backup key, anything protecting other credentials.

The characters-needed output works backwards from whatever you set:

• 80 bits → 13 characters with symbols, or 18 lowercase
• A smaller alphabet isn't a dead end. It just needs more characters, and those are usually easier to type and remember.

Don't trust a result of a few decades. Cracking rates only ever go up, and these numbers are a snapshot of hardware that'll look slow soon enough. A password isn't defending against today's attacker — it's defending against whoever holds your stolen hash in ten years. That's the case for being comfortably clear of the threshold rather than just past it.

The thing that makes all this real

Use a generator.

A password manager produces genuinely random strings, which is the only situation where the calculated entropy is the actual entropy. Everything on this page describes that case and only approximates any other. Our password generator does it in your browser.

And two things worth more than any amount of entropy: don't reuse passwords, and turn on two-factor where it's offered.