The buying guide
Protein powder portion size: calculate what is in your scoop
Scale nutrients by the ratio of powder used to the labeled serving weight. This tells you what the label implies for that portion; it does not tell you how much you should consume.
Use weight for a consistent calculation
Divide your chosen powder weight by the label's serving weight. Multiply each nutrient by that ratio. For a fictional 40 g serving containing 24 g protein, a 20 g portion contains a calculated 12 g protein.
Scoop shape and fill level are not part of the calculation. The tool needs the portion in grams, not a guess that one brand's scoop equals another's. Label rounding also limits the precision of the result.
Keep the rest of the drink separate
If you mix the powder with milk, a plant drink, yogurt, or other foods, those ingredients contribute their own nutrition. Add their label values separately if you are assessing the whole drink. Water changes the drink's volume but not the powder's nutrient amount.
Use the calculator to compare a portion already under consideration, including a portion discussed with your care team. It does not use age, body weight, or symptoms to generate a target, and it cannot determine whether a product meets an individual medical diet.