Answer
0.8 grams per kilogram of body mass
e.g. if you are 70 kg it is recommended that you have
70 kg x 0.8 grams protein per kg per day = 56 grams protein per day
However, it should be noted that this is the general rule for sedentary adults. It is widely agreed that up to 1.8 grams per kilogram of body mass are needed for active adults engaged in strength training or intense endurance training.