How much protein per day to build muscle?

The short answer: 1.6 to 2.2 g of protein per kilogram of body weight per day (about 0.7 to 1 g per pound). For someone who weighs 75 kg (165 lb), that's 120 to 165 g. That's the range that comes out of the most robust meta-analyses: the 2018 one (49 trials, 1,863 participants) puts the plateau for muscle gains at around 1.6 g/kg on average, and since the uncertainty extends up to 2.2 g/kg, its authors advise aiming that high so you leave nothing on the table. Beyond 2.2 g/kg, additional gains become undetectable in virtually everyone.

Forget absolute gram targets (“you need 150 g of protein”): everything is calculated per kilogram of body weight. And forget the “more is better” reflex: protein beyond your needs doesn't build more muscle; it's simply used as energy — expensive, filling energy, which can be useful when you're cutting, but not anabolic.

When do you need more protein?

• In a calorie deficit (cutting): go up to 2.2 to 2.6 g/kg. A 2014 systematic review puts the needs of lean, resistance-trained people in a deficit at 2.3 to 3.1 g per kilogram of lean mass, higher the more severe the deficit. When energy runs short, your body is tempted to draw on muscle; a high protein intake is your best insurance against muscle loss, along with heavy training and enough sleep — lack of sleep during a deficit melts lean mass at a spectacular rate.
• Past 50 to 60: “anabolic resistance” raises your needs — aim for the top of the range, with more generous servings at each meal. In men around 71 years old, muscle protein synthesis plateaued at about 0.40 g/kg per meal, compared with 0.24 g/kg at age 22.
• Vegetarian or plant-based: also aim for the top of the range, and vary your sources (legumes + grains + soy) to cover all the essential amino acids.

Does protein timing matter? A little

Your daily total does 80% of the work. The remaining 20%: spread it over at least 4 servings of about 0.4 g/kg (25 to 40 g for most people) — the target suggested by a 2018 review to reach at least 1.6 g/kg per day — each one providing enough leucine to trigger protein synthesis. The famous 30-minute post-workout “anabolic window” is a myth in its strict form: according to the International Society of Sports Nutrition, the anabolic effect of a session lasts at least 24 hours. A real meal within 2 to 3 hours after training is more than enough.

An often-overlooked point: the evening serving. According to the same scientific society, 30 to 40 g of slow-digesting protein (cottage cheese, casein) before bed increases overnight protein synthesis — and most of the repair happens during the night.

Is a high-protein diet bad for your kidneys?

In healthy people, a 2018 meta-analysis (28 trials, 1,358 participants) found no adverse effect of high-protein diets — 1.5 g/kg and above — on kidney function. Caution only applies if you already have kidney disease — and in that case, it's a conversation to have with a doctor, not with an article.

Key takeaways

• 1.6 to 2.2 g/kg/day to build muscle; 2.2 to 2.6 g/kg when cutting.
• Daily total first, distribution second: at least 4 servings of ~0.4 g/kg, including one in the evening.
• The strict anabolic window is a myth; consistency over months is what builds muscle.