Citrus fruits, such as grapefruit, contain citric acid. The exact amount of citric acid in one grapefruit will depend on a number of factors, most importantly the size of the fruit itself. By weight, grapefruits provide more citric acid than oranges but less than lemons or limes.
Citric Acid Content
Grapefruit juice contains about 25 grams of citric acid per liter, or 1,000 grams, of juice, according to a study published in the "Journal of Endourology" in March 2008. Each small grapefruit contains about 182 grams of juice, which means it has approximately 5 grams of citric acid. A medium grapefruit has about 233 grams of juice, so it provides approximately 6 grams of citric acid, and a large grapefruit contains about 302 grams of juice and provides approximately 8 grams of citric acid.