Free tool
Dry matter calculator for cat food
Type in the numbers from any cat food label. You’ll get phosphorus, protein, fat and sodium on a dry matter basis, plus mg of phosphorus per 100 kcal, the fairest way to compare wet and dry foods.
Phosphorus per 100 kcal
279mg
mg phosphorus per 100 kcal — for comparing foods, not a recommendation
279 mg phosphorus per 100 kcal.
Phosphorus DMB
1.14%
Protein DMB
45.5%
11.1 g / 100 kcal
Fat DMB
22.7%
Calories
898kcal/kg
Estimated
No calorie figure entered, so calories were estimated from protein and fat using modified Atwater factors. The real value can differ by 10% or more. Use the calorie statement on the label if there is one.
This calculator is for information only. It does not diagnose, stage or treat, and it is not a feeding recommendation. Ask your vet what phosphorus level is right for your cat.
Where to find the numbers
Look for the Guaranteed Analysis box on the can or bag. It lists crude protein (min), crude fat (min), crude fiber (max) and moisture (max). Some foods also list phosphorus and sodium. The calorie content statement, required on US cat foods, is usually just below, written as kcal/kg and kcal per can or cup.
Guaranteed analysis values are minimums and maximums, not exact amounts. A food listed as “phosphorus 0.2% min” might really contain more. For the most accurate picture, email the manufacturer and ask for the typical analysis (as fed) of phosphorus and sodium, and the calorie content.
A worked example
A pâté lists phosphorus 0.25%, moisture 78% and 1,000 kcal/kg. Dry matter is 100 − 78 = 22%. Phosphorus DMB is 0.25 ÷ 22 × 100 ≈ 1.14%. Per 100 kcal it is 0.25 × 1,000,000 ÷ 1,000 = 250 mg of phosphorus per 100 kcal.
Want to compare foods we’ve already calculated? Browse the phosphorus database.
How we calculate
US labels list nutrients as fed, including all the water. To compare foods fairly we convert them two ways:
- Dry matter basis (DMB) = as-fed % ÷ (100 − moisture %) × 100. This removes water, so a pâté and a kibble can be compared.
- mg per 100 kcal = as-fed % × 1,000,000 ÷ kcal per kg. Cats eat to meet their calorie needs, so this shows how much phosphorus comes with the energy they eat. We highlight this number.
When a food has no calorie statement we estimate calories with modified Atwater factors (3.5 kcal/g protein, 8.5 kcal/g fat, 3.5 kcal/g carbohydrate) and say so on the page. Estimates can be off by 10% or more.
We don’t label foods “low”, “moderate” or “high” in phosphorus: there is no accepted veterinary scale that says which number is right for an individual cat with CKD. We show the number, its source and how it was calculated, so you can compare foods and talk it through with your vet. A food’s phosphorus number alone doesn’t decide whether it’s right for your cat.
Try it yourself with the dry matter calculator, or read how to read a cat food label. Spotted an error? Email 781960591@qq.com.
Calculator FAQ
How do I calculate dry matter basis for cat food?
Subtract the moisture percentage from 100 to get the dry matter percentage. Then divide the nutrient’s as-fed percentage by the dry matter percentage and multiply by 100. For example, 0.25% phosphorus in a food with 78% moisture is 0.25 ÷ 22 × 100 ≈ 1.14% on a dry matter basis.
How do I convert phosphorus to mg per 100 kcal?
Multiply the as-fed phosphorus percentage by 1,000,000 and divide by the calories per kilogram. A food with 0.25% phosphorus and 1,000 kcal/kg has 250 mg of phosphorus per 100 kcal.
What if the label has no calorie statement?
The calculator estimates calories from protein, fat and an assumed carbohydrate content using modified Atwater factors, and clearly marks the result as estimated. Real values can differ by 10% or more, so use the label’s calorie statement whenever you can.
The KidneyPaw app
Skip the math in the aisle.
The KidneyPaw app scans a barcode and does this for you, then saves the foods your cat loves.