Math operations: different results from iOS emulator to real device.Maybe culture problems?

Hi,
I create an app with some calculation on distance between geoloc points.
On my emulator all works ( Region and Language are: Language English and Region United States ), but on my device ( region and language are italian ) the results are wrong.
I think a problem about of culture because I see in the app the number with the dot as comma that it the number are in US or EN culture.
How to manipulate the numbers independently by culture?