That's not an easy question to answer. It depends on the style of beer, how much carbonation you're looking for and the temp it will condition at.
I use Beersmith to calculate the amount of priming sugar consistent with the style. Usually about 4 oz per 5 gallons is given as a standard (sorry I didn't do the conversion to metric) but....like I said....it depends. How To Brew by Palmer has some good guidelines, and Beersmith can figure this out too.