# Protein efficiency ratio

Protein efficiency ratio (PER) is based on the weight gain of a test subject divided by its intake of a particular food protein during the test period.

From 1919 until very recently, the PER had been a widely used method for evaluating the quality of protein in food.

The food industry in the United States formerly used the PER as the standard for evaluating the protein quality of foods. The U.S. Food and Drug Administration now uses the PDCAAS as the basis for the percent of the U.S. recommended daily allowance (USRDA) for protein shown on food labels.

$PER \,= \frac{Gain\ in\ body\ mass(g)}{Protein\ intake (g)}$