See more from Ask Carzone 
How to change units in a Citroen C5 X?
how to change from kilometres to miles in Citroen C5X
Our answer:
Hi Tom,
You use the central touchscreen for this. Press the Settings menu, then the System tab. Within that screen you'll find various options, including the units of distance that can be altered.
Have a motoring question? Ask us here!
Ask us anything motoring related and please provide as much information as possible so we can give you the most accurate advice.