PRAL Calculator: Calculate Urine Acidity by Food
PRAL (Potential Renal Acid Load) was developed by Remer and Manz in 1995 and estimates how much acidity a food generates when metabolized, measured in mEq per 100 g. Positive values acidify urine (meats, cheeses, grains); negative values alkalinize it (fruits, vegetables). This calculator takes protein, phosphorus, potassium, magnesium, and calcium content (per 100g) and returns the food's PRAL score. Useful for managing uric acid kidney stones, osteoporosis, and gout.
When to use this calculator
- You have uric acid or cystine kidney stones and need to alkalinize your urine.
- Your doctor mentioned low urine pH and you want to adjust it through diet.
- You have gout and want to reduce acid load without extra medication.
- You want to estimate whether your diet is net acidic or alkaline.
- You study renal physiology or nutrition and need a practical tool.
Example: 100 g beef
- Protein = 25 g, P = 180 mg, K = 300 mg, Mg = 20 mg, Ca = 12 mg.
- PRAL = 0.49×25 + 0.037×180 − 0.021×300 − 0.026×20 − 0.013×12.
- PRAL = 12.25 + 6.66 − 6.3 − 0.52 − 0.156 ≈ +11.9.
- Beef generates acidic urine.
How it works
1 min readPRAL Formula
PRAL (mEq/100g) = 0.49×Protein(g) + 0.037×Phosphorus(mg)
− 0.021×Potassium(mg) − 0.026×Magnesium(mg) − 0.013×Calcium(mg)PRAL by Food
| Food | PRAL |
|---|---|
| Parmesan cheese | +34 |
| Tuna | +15 |
| Beef | +12 |
| Chicken | +9 |
| Egg | +8 |
| White bread | +3.7 |
| Milk | +0.7 |
| Rice | +1.7 |
| Tomato | −3.1 |
| Apple | −2.2 |
| Banana | −5.5 |
| Spinach | −14 |
| Raisins | −21 |
| Avocado | −8 |
| Broccoli | −4 |
Interpretation
Clinical Applications
1. Uric acid/cystine kidney stones: Alkaline urine (pH >6.5) prevents formation. Favor negative PRAL foods.
2. Osteoporosis: High PRAL diets increase urinary calcium losses from bone.
3. Gout: Reducing total daily PRAL can help lower uric acid levels.
4. Chronic kidney disease (Stage 3–5): Adjust acid load with nephrologist guidance.
Daily PRAL Calculation
Sum the PRAL of all foods eaten in a day. Target: net PRAL between −10 and +10.
Consult a nephrologist or registered dietitian. Values are for guidance only.
Frequently asked questions
What is PRAL and why does it matter?
PRAL (Potential Renal Acid Load) measures how much acid or alkaline a food produces in your body after digestion. It matters because a high-acid diet can increase kidney stone risk, worsen gout, and contribute to bone loss over time.
How do I calculate my daily PRAL?
Look up or measure the protein, phosphorus, potassium, magnesium, and calcium content of each food you eat, calculate the PRAL for each using the formula, then sum all values. Aim for a net daily total between −10 and +10.
Which foods are most acidifying?
Parmesan cheese (+34), tuna (+15), beef (+12), and other animal proteins rank highest. Grains and refined carbohydrates are also moderately acidifying.
Why do citrus fruits alkalinize despite tasting acidic?
Despite their acidic taste, citrus fruits actually alkalinize urine. Lemon has a PRAL of about −2.5 because its minerals (potassium, magnesium) override the acidity of citric acid during metabolism.
Does a vegetarian diet reduce PRAL?
Yes, most vegetarian and vegan diets have negative net PRAL because they emphasize fruits, vegetables, legumes, and nuts—all rich in potassium, magnesium, and calcium.
Where do I find nutrient data for foods?
USDA FoodData Central (fdc.nal.usda.gov), food package labels, or nutrition apps like Cronometer. Most databases list protein, phosphorus, potassium, magnesium, and calcium per 100g.
Can I use PRAL if I have advanced kidney disease?
PRAL is useful, but advanced CKD requires careful potassium and phosphorus restriction. Always work with your nephrologist before making dietary changes—do not self-treat.
How does PRAL relate to urine pH?
PRAL estimates the net acid or base your kidneys must excrete. Higher PRAL tends to lower urine pH (more acidic); negative PRAL raises it (more alkaline).