You’ve probably punched one in today. Maybe it was to unlock your phone, pay for a coffee, or get into your gym locker. We’re talking about all possible 4 digit codes. It seems like a simple concept, right? Just four numbers. But those four slots represent a massive gateway between your private life and the rest of the world.
There are exactly 10,000 combinations. That’s it. From 0000 to 9999. It’s a finite sandbox. Yet, within that small range, human psychology, mathematical probability, and security flaws collide in some really weird ways. Most people think their PIN is unique. Most people are wrong.
The Math Behind the 10,000 Combinations
Let's look at the raw numbers. Since each position in a four-digit code can be any digit from 0 to 9, you calculate the total by multiplying the possibilities for each slot: $10 \times 10 \times 10 \times 10 = 10,000$.
If you were to guess a random code on your first try, you have a 1 in 10,000 chance. That’s 0.01%. Not great odds for a thief, but not impossible either. Especially when you realize humans aren't random. We are incredibly predictable. We like patterns. We like birthdays. We like things that are easy to remember while we're rushing through a checkout line.
Why Some Codes Are "Heavy"
Data scientist Nick Berry, formerly of Data Genetics, conducted a famous analysis of leaked passwords and PINs. He found something staggering. Out of all possible 4 digit codes, the most common one—1234—accounted for nearly 11% of the dataset.
Think about that.
If a thief finds a lost wallet, they don't need to try 10,000 combinations. They just need to try the top 10. If they do, they have about a 20% to 25% chance of getting in. It’s wild how often people choose 1111 or 0000. These are the "heavy" codes. They appear in the wild far more often than "light" codes like 8068 or 7043, which have no obvious pattern and aren't tied to common years.
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The Psychology of Selection: Why You Chose Your PIN
Humans are terrible at being random. If I asked you to pick a number between 1 and 100, you’d probably pick 17, 42, or 69. When it comes to all possible 4 digit codes, we tend to follow specific "mental maps."
Most people use years. Specifically, years starting with 19 or 20. If your PIN starts with 19, you’ve instantly narrowed the search space for a hacker from 10,000 down to about 100. They’ll guess 1970 through 1999 and probably hit the jackpot. People also love "couplets." 1010, 1212, 6969.
Then there's the tactile pattern. On a standard 3x3 keypad, people pick shapes. A straight line down the middle (2580). The four corners (1379). It’s easier for our muscle memory. But security isn't about ease; it's about friction. If your finger moves in a way that feels "natural" on the keypad, a sophisticated observer can likely guess your code just by watching the angle of your hand.
Security Realities and the "Birthday Paradox"
You’ve likely heard of the Birthday Paradox. In a room of just 23 people, there’s a 50% chance two of them share a birthday. PINs work similarly in a social context. Because so many people use MM/DD or DD/MM formats for their codes, the pool of "active" codes used by the general population is much smaller than the theoretical 10,000.
If you use your birthday, you aren't choosing from 10,000 options. You’re choosing from 366.
Banks know this. Some high-security systems actually block you from using the most common codes. If you try to set your bank PIN to 1234 or your birth year, the system might kick it back. They are forcing you into the "long tail" of the probability curve.
Digital Locks vs. Physical Keypads
There is a difference between how these codes are used on a smartphone versus a physical gate or a "dumb" safe. Your iPhone has a lockout mechanism. After a few wrong tries, it adds a time delay. Eventually, it wipes the data. This makes a brute-force attack—trying every single one of all possible 4 digit codes—physically impossible.
Physical keypads on cheap home safes or gates often don't have this. A persistent intruder can sit there and click through 1,000 combinations in an hour. This is why 4-digit codes are increasingly being replaced by 6-digit codes or biometric scans. Adding just two more digits moves the needle from 10,000 possibilities to 1,000,000.
The Evolution of the 4-Digit Standard
Why 4 digits? Why not 5 or 3? We owe this to James Goodfellow, the Scotsman who invented the Personal Identification Number in the 1960s. Legend has it he originally wanted 6 digits. However, his wife, Caroline, told him she could only remember 4.
That one observation by a frustrated spouse set the global standard for the next sixty years. It’s a classic case of "user experience" trumping "security protocol." We’ve been living in Caroline’s memory limit ever since.
Common Misconceptions About PIN Safety
People think that changing one digit makes them safe. "Oh, I'll use 1235 instead of 1234." Hackers use "neighboring" scripts that check for these slight variations.
Another mistake: thinking that "random" looking patterns like 2580 are safe. As mentioned, 2580 is the middle column of a keypad. It’s one of the top 15 most common PINs.
Wait, is 0000 actually bad? Surprisingly, some experts argue that if you’re going to pick a common PIN, 0000 is slightly better than 1234 because people often overlook the absolute obvious in favor of the "slightly" hidden. But honestly? Just don't do it.
How to Pick a Code That Actually Works
If you want to be safe within the constraints of all possible 4 digit codes, you have to think like a machine, not a human.
- Avoid the 19xx and 20xx start. Stop using birth years or graduation years.
- Break the visual pattern. Don't make a square, a line, or a cross on the keypad.
- Use a "memory anchor" that isn't a date. Think of a word, like "JEEP." On a phone keypad, J-E-E-P translates to 5-3-3-7. That’s much harder to guess than your anniversary.
- Avoid repeating digits. 7788 or 1122 are easy to spot by looking at fingerprint smudges on a screen.
The Future of the Four-Digit Code
Are we moving away from them? Definitely. Between FaceID, TouchID, and 2FA (Two-Factor Authentication), the 4-digit PIN is becoming a "fallback" rather than the primary shield. But it’s not dead yet.
It survives because it’s the lowest common denominator. It’s the backup for when the camera can’t see your face in the dark or your fingers are wet. It is the universal language of access.
Understanding the distribution of these 10,000 numbers is about understanding human behavior. We are creatures of habit. We want the shortest path to our goal. But when that goal is security, the shortest path is usually the most dangerous one.
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Actionable Steps for Better Security
Instead of just worrying about your PIN, take these concrete steps today:
- Check your most vital accounts. If your primary bank or email uses a 4-digit code, see if you can upgrade to 6 digits or an alphanumeric password.
- Clean your screens. Seriously. Fingerprint oils on a touch screen often give away the four digits you use, even if the observer doesn't know the order.
- Use the "Random Number Generator" test. Use a tool to generate a random 4-digit number. If it feels "weird" or "hard to remember," it’s probably a good code. Write it down in a secure password manager like Bitwarden or 1Password until you've memorized it.
- Look for wear and tear. On physical buttons, if the 1, 2, 3, and 4 keys are shinier or more worn than the others, it’s a dead giveaway. Change the code to include less-used numbers like 7, 8, or 0.
By moving your PIN choice into the "boring" and "random" sectors of the 10,000 possible combinations, you effectively disappear from the radar of most low-level attackers. Be the 8068 in a world of 1234s.