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PRAL Acid Load Calculator

Enter the nutrient amounts to get the PRAL.

How it is calculated

The tool adds protein and phosphorus, which push the load up, and subtracts potassium, magnesium and calcium, which pull it down: PRAL = 0.49×protein + 0.037×phosphorus − 0.021×potassium − 0.026×magnesium − 0.013×calcium. Protein is in grams; phosphorus, potassium, magnesium and calcium are in milligrams. The result is in mEq with two decimals. Any field left empty counts as 0, and the tool needs at least one field filled in; entering only protein, for example, simply returns 0.49 × protein. The coefficients are fixed and the tool does not check whether your intake figures are realistic, so the quality of the answer depends on the nutrient totals you take from a food label or database.

Worked example

A day with 90 g protein, 1400 mg phosphorus, 2800 mg potassium, 300 mg magnesium and 800 mg calcium. Protein: 0.49 × 90 = 44.10. Phosphorus: 0.037 × 1400 = 51.80. Potassium: 0.021 × 2800 = 58.80 subtracted. Magnesium: 0.026 × 300 = 7.80 subtracted. Calcium: 0.013 × 800 = 10.40 subtracted. Total: 44.10 + 51.80 − 58.80 − 7.80 − 10.40 = 18.90 mEq, a net acid-forming result.

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Common mistakes

  • Entering minerals in grams instead of milligrams. Potassium of 2.8 (grams) instead of 2800 (mg) makes the base-forming part disappear and the PRAL look strongly acidic.
  • Entering protein in milligrams or as a percentage of calories. The field is grams per day.
  • Leaving potassium, magnesium or calcium blank because the label does not list it. Blank counts as 0, so the result is higher than the real figure.
  • Using values per 100 g of one food and then comparing with a daily PRAL. The number is per whatever quantity you enter, so keep the same basis (one food or a whole day).
  • Treating the figure as medical advice. It estimates acid load from five nutrients only; a person on a renal diet should follow their clinician's targets.

Sources

About this calculator

PRAL (potential renal acid load) is a formula developed by Remer and Manz (1995) that estimates whether a food or diet will produce a net acid or net alkaline load for the kidneys to excrete: PRAL (mEq/day) = 0.49×protein(g) + 0.037×phosphorus(mg) − 0.021×potassium(mg) − 0.026×magnesium(mg) − 0.013×calcium(mg). A positive value means the food is acid-forming (mostly meat, fish, cheese, and grains), while a negative value means it's alkaline-forming (mostly fruits and vegetables).

Dietitians, nephrology patients on renal diets, and followers of the alkaline diet use PRAL to select foods that reduce dietary acid load, since a chronically high acid load has been linked to bone mineral loss and is a factor clinicians weigh in chronic kidney disease management.

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