Why Phone Keypads and Calculator Keypads Differ

I won't say I've often wondered, but I've sometimes had occasion to wonder why touch-tone phones and calculator have different number layouts. Both devices have digits 0-9, laid out in three rows... yet, "1" is on the top of the phone keypad and on the bottom of the calculator keypad.

The Calculator Reference has 3 pundits weigh in regarding why these everyday devices differ in this subtle (and nerdy) way.

In a nutshell: The calculator was laid out first. There are many reasons why the phone's layout is different. Perhaps the strongest rationale for placing "1" at the top of a touch-tone phone was to make its layout akin to the number layout of the rotary phone.