text: why is a british 'billion' worth 1 thousand million and what is a us billion worth ? why are they different ? in the old british system, 1 million = 1*10^6 or 1000000 and a 1 milliard = 1*10^9 or 1000000000 so 1 billiion=1*10^12 or 1000000000000  in the metric system,  1 million=1*10^6 or 1000000 1 billion=1*10^9 or 1000000000  its been unified now, and the milliard unit discarded. not entirely sure why, but its probably to do with non british wealthy types wanting to sound wealthier... or something :-)