How many grams is 3 oz of protein? A guide to measuring your intake
                                
                                
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                                    3 min read                                
                            
                                According to nutrition experts at Johns Hopkins, a serving of cooked poultry, beef, or fish the size of a deck of cards is approximately 3 ounces, which contains about 21 grams of protein. The exact number of grams in a 3 oz serving of protein can vary significantly depending on the food source, from lean meats to plant-based options.