Google's calculator calls that 1 mile.

I think that conversion was defined the wrong way around in his program, trying to use 1 cm=0.3937" which is wrong.

1.609344 km = 1609.344 m = 1760 * 0.9144 m = 1760 yards = 1 mile by definition through the definition of the yard as 0.9144 m

Just checked, using 1cm=0.3937" is wrong in the wrong direction and makes it 0.999998 mile.

I have no idea what goes wrong with his program other than obviously using insufficient precision for the number of digits presented.

__________________
‘To those who regard “crime fiction” as some sacred icon which must follow a rigid formula, I will always be the man who writes 18-syllable haiku.’Trying to make sense of computers, The Error Log.