How Much Protein Per Day for Muscle Growth? The Science Explained

How much protein per day for muscle growth?

You train hard, sleep enough, and eat "healthy." But are you actually building muscle? There's a good chance your protein intake makes the difference. Yet you hear different numbers everywhere: 1.2 grams per kilo, 2 grams per kilo, 3 grams if you're serious. So what's actually correct?

In this article, we explain what science says about protein intake for muscle growth. No vague advice, just concrete guidelines based on research.

Why protein matters so much for your muscles

Muscles are largely made up of proteins. When you train, you damage muscle fibers (in a good way). Your body repairs those fibers and makes them stronger. But that repair process needs building blocks, and those building blocks are amino acids. They come from protein.

Without enough protein, your body can't properly complete the repair process. You're training, but the growth lags behind. That's a waste of your effort.

Proteins consist of 20 amino acids, of which 9 are essential. You need to get those through food. Leucine is the most important one for muscle protein synthesis, the process where your body creates new muscle proteins (Devries & Phillips, 2015).

The scientific guideline: 1.6 to 2.2 grams per kilo

The most cited meta-analysis in this field comes from Morton et al. (2018), published in the British Journal of Sports Medicine. The researchers analyzed 49 studies with a total of 1,863 participants. Their conclusion: a daily protein intake of at least 1.6 grams per kilogram of body weight is needed to achieve maximum muscle growth in people doing resistance training (Morton et al., 2018).

More than 2.2 grams per kilo showed no additional benefit for muscle growth in the studied research. That doesn't mean it's harmful, but it won't make your muscles grow faster.

The sweet spot is between 1.6 and 2.2 grams of protein per kilogram of body weight per day.

What does that look like in practice?

70 kg (154 lbs): 112 to 154 grams of protein per day
80 kg (176 lbs): 128 to 176 grams of protein per day
90 kg (198 lbs): 144 to 198 grams of protein per day
100 kg (220 lbs): 160 to 220 grams of protein per day

Want to know exactly how much protein you need? Use our protein calculator to determine your personal requirements.

Does the protein source matter?

Yes, but less than you might think. Animal proteins (meat, fish, dairy, eggs) contain all essential amino acids in good ratios. Plant-based sources sometimes lack one or more amino acids, but by combining them (rice + beans, bread + peanut butter) you can easily solve that.

A study by Hevia-Larraín et al. (2021) showed that plant-based protein can be just as effective as animal protein for muscle building, as long as total intake is high enough (Hevia-Larraín et al., 2021).

The best protein sources for muscle building:

Chicken breast (31g protein per 100g)
Greek yogurt (10-12g per 100g)
Eggs (13g per 100g)
Tuna (26g per 100g)
Whey protein (70-80g per 100g powder)
Lentils (9g per 100g cooked)
Tofu (12g per 100g)

Timing: when should you eat your protein?

For a long time, we thought you had to eat protein within 30 minutes after your workout. That "anabolic window" turns out to be much less strict than we believed.

What does matter: how you distribute your protein throughout the day. Schoenfeld and Aragon (2018) concluded that spreading your protein intake across 3 to 5 meals per day is better for muscle protein synthesis than cramming everything into 1 or 2 meals (Schoenfeld & Aragon, 2018).

A good rule of thumb: eat a meal with at least 20-40 grams of protein every 3 to 5 hours. That keeps muscle protein synthesis active throughout the day.

Example daily schedule (80 kg, goal: 160g protein)

Breakfast (07:00): 3 eggs + whole grain bread + yogurt = ~35g
Lunch (12:00): Chicken breast wrap + salad = ~40g
Snack (15:30): Whey shake = ~25g
Dinner (18:30): Salmon + rice + vegetables = ~40g
Evening snack (21:00): Yogurt with nuts = ~25g

Total: 165 grams of protein, spread across 5 moments. Achievable and effective.

Common mistakes with protein intake

1. Too little protein at breakfast

Most people eat toast with jam or a croissant for breakfast. That gives you maybe 5-8 grams of protein. You start the day at a disadvantage. Add yogurt, eggs, or a shake to your morning.

2. Cramming everything into one meal

A huge chicken-and-rice meal after your workout isn't wrong, but your body can only optimally use a limited amount of protein per meal for muscle synthesis. Spread it out instead.

3. Relying only on supplements

Whey protein is convenient as a supplement, but it doesn't replace proper meals. Whole foods also contain vitamins, minerals, and fiber that you need. Use supplements as additions, not as your foundation.

4. Ignoring your calories

Protein alone isn't enough. If your total calorie intake is too low, your body uses protein as fuel instead of building material. Make sure you eat enough to support your training.

Do you need more protein during a cut?

Yes. During a caloric deficit, the risk of muscle loss is greater. Helms et al. (2014) recommend a protein intake of 2.3 to 3.1 grams per kilogram of lean body mass for athletes in a cut (Helms et al., 2014).

That's higher than the standard 1.6-2.2 grams per kilo of total body weight. The reason: with fewer calories, you want to give your muscles extra protection against breakdown. More protein helps with that.

Is too much protein harmful?

A persistent myth is that high protein intake is bad for your kidneys. In healthy people, there's no evidence for this. A year-long study by Antonio et al. (2016) had participants eat 3.3 grams of protein per kilo with no negative effects on kidney or liver function (Antonio et al., 2016).

Do you have an existing kidney condition? Then consult your doctor. But for healthy athletes, high protein intake is safe.

The role of whey protein

Whey protein is one of the most researched supplements in the world. It's quickly absorbed, has a high leucine content, and is easy to use. For people who struggle to get enough protein from food, it's a practical solution.

Not all whey is equal. There are big differences in protein content, taste, purity, and price. At WheyWijzer, we compare the most popular whey proteins so you can make an informed choice.

Summary

Let's put it all together:

Aim for 1.6 to 2.2 grams of protein per kilogram of body weight per day for muscle growth
During a cut, go towards 2.3-3.1 grams per kilo of lean body mass
Spread your protein across 3 to 5 meals per day
The source matters less than the total amount
Whey protein is a handy supplement, not a replacement
High protein intake is safe for healthy people

Want to know exactly how much protein you need? Try our free protein calculator.

Sources

Morton RW, et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine. PubMed
Devries MC, Phillips SM (2015). Supplemental protein in support of muscle mass and health: advantage whey. Journal of Food Science. PubMed
Hevia-Larraín V, et al. (2021). High-Protein Plant-Based Diet Versus a Protein-Matched Omnivorous Diet. Sports Medicine. PubMed
Schoenfeld BJ, Aragon AA (2018). How much protein can the body use in a single meal for muscle-building? Journal of the International Society of Sports Nutrition. PubMed
Helms ER, et al. (2014). Evidence-based recommendations for natural bodybuilding contest preparation. Journal of the International Society of Sports Nutrition. PubMed
Antonio J, et al. (2016). A High Protein Diet Has No Harmful Effects: A One-Year Crossover Study in Resistance-Trained Males. Journal of Nutrition and Metabolism. PubMed