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I came across this on the web. It's supposed to be funny, but we all know better :)

enter image description here

So, why are the numpad layouts different, and what are the reasons behind each?

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Thanks for a fun & easy weekend question. =) –  dnbrv Jan 28 '12 at 16:18
+1 to you sir; I too have so often wondered this and been frustrated by it. –  Bernhard Hofmann Jan 28 '12 at 17:38
What's really going to bake your noodle later on is, why is the zero placed at the bottom in both layouts?! –  Rahul Jan 29 '12 at 11:52
@Rahul I'm actually pretty sure about that one :). On the kbd it's because it's the most frequently used digit (in "real-life" numbers but not in phone numbers), and on the phone - so as to not break apart the row of *0# - which would be bad for all kinds of reasons. And you're not going to place that row above the other digits, because it's hardly ever used. –  Vitaly Mijiritsky Jan 29 '12 at 17:16
@Rahul Gotta love a Matrix reference! +1 –  Jeremy Miller Jan 24 '14 at 4:48

5 Answers 5

up vote 53 down vote accepted

There's this humongous article called Keyboard Trivia that has collected many of the theories and stories. The summary of facts:

  • Touch-tone key pad was designed to mimic the rotary dial with the "1" on top and the 7-8-9 on the bottom, and AT&T conducted user testing to confirm that this configuration helped eliminate dialing errors.
  • By the time when the touch-tone telephone was being designed in the late 1950s, the calculator and adding-machine designers had already established a layout that had 7, 8 and 9 across the top row.
  • Back then, the industry-standard typical calculator had nine columns of numbers, with 10 numbers in a column, the lowest digits at the bottom, starting with 0 and moving up to 9, and was basically a mechanical adding machine that closely resembled a cash register.
  • It is common practice today to use the telephone-keypad layout when designing new products that utilize a keypad, such as Automated Teller Machines.
  • When Bell Labs began exploring keypad layouts in the late 1950s they contacted all of the leading calculator manufacturers to find out why they had chosen to put low numbers at the bottom and high numbers at the top rather than the other way around. The answer, apparently, was a big shrug. It turns out that decision was largely arbitrary: no one had done any research about which layout was most convenient for users. Still, when it came time to place a numeric keypad on a computer keyboard, the calculator model with 7-8-9 at the top prevailed.

There's also a theory that phone engineers wanted to slow down people who were fast at entering numerical data, which would jam lines and produce dialing errors, so they reversed the layout. However, records of AT&T Labs' research clearly invalidate it.

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In a left to right / top to bottom culture the telephone layout is more logical...123,456,789 –  PhillipW Jan 28 '12 at 20:26
@PhillipW: That's what the AT&T research has shown. –  dnbrv Jan 28 '12 at 20:49
PhilipW: tell that to an accountant that is subject to Benford's law en.wikipedia.org/wiki/Benford's_law –  Kris Van Bael Feb 1 '12 at 6:25
Here's a video explaining Bell Labs' usability studies which led to the decision. wimp.com/phonebuttons –  Patrick McElhaney Sep 13 '13 at 16:44
isn't it a hypothesis rather than a theory about the phone engineers, i.e. something that might be true, or makes sense, sounds possible etc, but has no evidence (yet), whereas theories are often the best interpretation of a wealth of evidence and actually very close to fact in many cases ? –  Toni Leigh Jan 16 '14 at 8:26

One additional possible explanation is that with the calculator layout many calculations can be performed along the bottom two rows and the plus button only; zeroes, decimal points and the enter/equals button.

Since the main buttons are all at the bottom, it makes reasonable sense that the other numbers would count up from the bottom too.

I suspect (but have no proof) that the phone keypad layout would make typing on a calculator more difficult for most simple calculations.

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The proof lies in Fitt's Law plus Zipf's Law. Zipf's Law states that low numbers (0,1,2,3) are much more common in random numeric data than high numbers. Fitt's Law states that it takes longer to hit buttons that are further away...and hand position means the bottom row is closer. –  Alex Feinman Jan 14 '13 at 20:28
@AlexFeinman: do you mean Benford's law? Zipf's law is about the distribution of words, not numbers. –  Kit Grose Jan 17 '13 at 0:00
I do! Thanks for the correction. The two laws are functionally similar, but have different implications. –  Alex Feinman Jan 17 '13 at 13:54

I have a reasonable explanation. Since I come from mathematics background, this is the first thing that comes to mind.


You probably have heard of the Benford's law, also known as the "First digit law". It says, that digits 1,2,3 occur more often than 7,8,9 when dealing with random, arbitrarily big numbers, which numbers that users type into calculators, in fact, are.

The graph is something like this and shows heavy bias against the digit "1". Therefore it's sensible to put digits 1, 2, and 3 to the bottom row, as it's closer to the enter and also user reaches them easier.

enter image description here Benford's law (wikipedia)

Phone numbers

Since phone numbers are have limited number of digits and are in fact, randomly scattered, the Benford's law doesn't apply here, which means all the digits occur with similar frequencies. This might be the reason that the more natural ordering is used, since there's no reason to complicate.

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I am sorry but could not understand the connection between the question and your answer. What about the zero btw? –  Abektes May 27 '14 at 14:38

*In the early sixties I took a year out of university and got a job in the internal audit department at the head office of a large insurance company in Toronto. A substantial part of my job involved using an electromechanical calculator to check figures submitted by various departments. The keyboard layout was identical to present computer layouts as well present digital calculators. Index finger was for the left column, next two for adjacent ones. Thumb did zeros exclusively. I became very fast at this touch based skill, as my eyes were on the numbers on paper (there was no visual feedback - just the numbers that were printing on the tape, but you didn't look at that. Mistakes were extremely rare, and required a redo of the entire document. This was also in the days of rotary phones. Imagine my shock when reversed digital keys appeared on telephones. My skill was not transferable to them. The decision by Bell Labs, or whomever, to reverse the layout was thoughtless at best, stupid at worst.

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Also: you tend to hold the device at a different angle. You might use all five fingers on a keyboard numpad, but on your phone only your thumb (or the index finger of the hand not holding the phone)..

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Does this fundamentally affect the layout choice though? In both situations, I need to use all of the keys available, and experience no bias toward higher or lower numbers. –  doppelgreener Jan 20 '14 at 6:58

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