Well, first things first, you would need to know what is the estimated ideal adult weight for your pup, ie how much would your pup weigh (roughly) when he is bigger. From there, you would need to determine the percentage of how much to feed based on the weight.

For example, Scottie is about 6+kg now (he is going to be 2 years old this year). The ideal weight for a Min Schnauzer is about 5.4 to 6.8 kg (Wikipedia), so I put Scottie's ideal weight as 6kg. From there, I give him 2% of his body weight in amount of food (coz he's still a bit chubby) which is about 120g per day.

For puppies, they should definitely take more than 2% coz they're growing fast. A puppy can be fed up to 4% of the ideal adult weight if the puppy is very active and not too chubby... Ultimately, it's up to us as the owners to 'Know Our Dogs' and monitor them constantly. If the pup is chubby, feed less and if he is too skinny, up the amount. Hope that helps!