Amount of extra protein required to build muscle

Skeletal muscle is approximately 72% water, 22% protein, and 6% fat, glycogen, and minerals. One pound (~ 0.45g) of muscle tissue contains ~ 100g of protein. In order to gain 1 lb of lean mass per week, an athlete would have to ingest an extra 14g of protein per day (100g/7 days). This calculation seems easy but in practice, it is not that simple. Most experts believe that the single most important factor in gaining lean mass (along with resistance training) is to consume a hyperenergetic or excess calories diet. The individual should consume an additional 200-400 kcal/day (3-5kcal/kg/day) above maintenance requirements in addition to consuming the extra protein intakes as recommended.

References:

Antonio, J., Kalman, D., Stout, J. R., Greenwood, M., Willoughby, D. S., & Haff, G. G. (Eds.). (2008). Protein. In A. Ziegenfuss,T.N. and Landis, J. (Eds.),  Essentials of sports nutrition and supplements (pp. 259). Chapter Humana Press.