Muscles are mainly made up of protein.
Like most body tissues, muscle is dynamic and is constantly being broken down and rebuilt.
Building Muscle Requires More Protein
To build muscle, your body has to make more muscle protein than it breaks down.
In other words, your body needs a net positive balance of protein - often referred to as a nitrogen balance because of the high nitrogen content in protein.
As a result, people who want to build muscle generally eat more protein alongside their exercise routine. A higher intake of protein helps to build muscle and strength.
Maintaining Muscle Requires More Protein
At the same time, people who want to maintain the muscle they have built may need to continue their increased protein intake, as high protein intake during fat loss can prevent the muscle loss that often occurs when dieting.
How Much Protein Is Recommended
When it comes to muscle mass, studies generally look at the number of grams of protein per kilogram/pound of body weight, rather than the percentage of calories from protein.
In general, the recommendation for muscle development is 1 gram of protein per pound of body weight or 2.2 grams per kg of body weight.
Many studies have attempted to determine the optimal amount of protein for building muscle, but many have reached varying conclusions
It is difficult to give an exact figure because of conflicting studies, but about 0.7 to 1 gram per pound of body weight (1.6 to 2.2 grams per kilogram) seems to be a reasonable estimate.
If you have a lot of body fat, you may want to use your lean body mass or target body weight rather than your current body weight.
Summary TL;DR
If you want to gain and/or maintain muscle mass, it is important to consume enough protein. Most studies suggest that 0.7 to 1 gram per pound (1.6 to 2.2 grams per kilogram) of lean muscle mass is sufficient.
