Why are the numbers on calculator pads and telephones reversed? 
Calculators start w/1 at the bottom of the pad & telephone pads start
w/1 at the top line.

I hope a researcher can provide a definitive answer to this question -
it certainly is a puzzling and irritating phenomenon. My own guess is
that because 'phone keypads have letters on them (and are derived from
the original dials which had letters on them) they are arranged in the
same way as printing on paper - ie from top to bottom. However, with
calculators, which solely have numbers, the keys are arranged in a way
logical for numbers - with the lowest at the bottom, and the highest
at the top. I'm not sure I'm convinced myself; but it's the best I can
come up with!

I was told by Ma Bell that they were reversed due to accountants
ability to enter numbers faster than the "old" pulse style phone could
process. for what that is worth.

The real answer seems to lie in a study conducted at Bell Labs titled
?Human Factor Engineering Studies of the Design and Use of Pushbutton
Telephone Sets.? Published in the July 1960 ..........
http://www.vcalc.net/Keyboard.htm

just theories
http://www.straightdope.com/mailbag/mphonedial.html