Have you ever wondered why ATM PINs have 4 digit Code only? Here is why!

The reason behind ATM’s 4 digit pin code

You walk into your friendly neighborhood ATM kiosk and swipe your card. You then punch in a 4-digit PIN code to authenticate yourself and proceed to withdraw money. You may have been doing this mechanically since the day ATM was introduced but have you given a thought why ATM PINs have a 4 digit code?  No! Then read on..

Automated Teller Machines (ATM) were first introduced in 1967 and now have emerged as a best option to disburse cash. Instead of visiting your bank and waiting in a long queue to withdraw money, you just have to swipe your ATM card, punch in your secret 4 digit PIN and take away the money you require.

But if someone has found or steal your card, the only barrier protecting your money is your 4-digit ATM PIN. Ever wondered why most PINs have only 4 digits? Given that an ATM dishes out money, wouldn’t the manufacturers of ATMS have been wiser to introduce a longish PIN say six digit or eight digit one. Isn’t that why our email passwords are also expected to be 6 letters or more?

You see there is a bit of story behind it. ATM was invented by a well known Scottish inventor John Adrian Shepherd-Barron, the man who pioneered the development of the ATM machine. Barron was born in Shillong and was son to a Wimbledon ladies doubles champion, Dorothy Barron. When testing out his invention, Barron had also proposed a 6-digit PIN.

However, the first person to use his invention was his wife, Caroline. We all know that behind every successful man is a woman, and Caroline apparently rejected the idea of using a six code PIN for her husband’s invention because she could only remember the numbers up to four.

When Barron came up with the idea when he realised that he could remember his six-figure army number. But he decided to check that with his wife, Caroline.

“Over the kitchen table, she said she could only remember four figures, so because of her, four figures became the world standard,” he laughs.

Reportedly, 6 numbers stringed together were too much information for her to recall.

Although, there are many banks nowadays that offer 6 digit PINs for security purposes, shouldn’t those of us using 4 digit PINs be thanking Caroline? It gets tough to recall those 4 digits at times, imagine what 6 or more would do to us?


  1. I expected a pretty factful mathematic and technical explanation to this question..

    However if this article was presented more technically, would have given a great knowledge to masses and created an awareness why one should regularly change ATM pins for safety.

  2. What BS!!! My ATM/Debit card has 6 digit pin. If you don’t believe check with HSBC. They have always been issuing 6 digit pins

    • “Although, there are many banks nowadays that offer 6 digit PINs for security purposes, shouldn’t those of us using 4 digit PINs be thanking Caroline?”

  3. I thought you would give us some technical information about why atm pin are 4 digit. But now I think I wasted 5 mins of my life.

    I’m un following your facebook page because all your posts are bulls hit doesn’t make any scence.

    Good bye


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