For natural lifters this is fairly straightforward, but probably also varies a little bit due to people’s bodies being different.
General Rule(s) of thumb:
Cutting: ~1g per 1 lb of body weight or 2.2g per 1 kg of body weight.
If you’re looking to drop weight, chances are you’re trying to lose fat and not muscle. You lose weight by being in a caloric deficit and your body burns stored energy in order to fuel your staying alive. If you don’t have enough protein, your muscles will go catabolic on you (breakdown for the sake of energy) and your cut will be pointless. There will always be some muscle loss in cutting, but you can severely reduce it by eating enough protein.
- For muscle loss research, see: https://ncbi.nlm.nih.gov/pubmed/19927027
- More specific to caloric deficit: https://ncbi.nlm.nih.gov/pubmed/24864135
Bulking: ~0.8g per 1 lb of body weight or 1.76g per 1 kg of body weight.
Bulking is fairly straightforward. You’re getting enough calories, so you don’t have to worry about getting enough protein for your muscles to not disappear, just enough to make sure they’re growing adequately. For a natural, non-enhanced, lifter, 0.8:1 seems to be the magic ratio. Eat your protein, make sure you’re getting enough fat and then load up on some carbs.
For more detailed analysis of nutrition/weightlifting studies, check out @iwannaburnfat on IG. It’s certainly no TL;DR, but he’s the guy I followed that got me started looking at studies and such. Dude does his homework.