I was reading this article about using moisture to convert other percentages into their dry matter basis. The article is here: http://www.dogfoodadvisor.com/choosing-dog-food/dry-matter-basis/

But it doesn't go into how to convert ones that don't end in a percentage.

For example, take analysis for dog food

How would I convert Vitamin A 19000 IU/kg or 150,000,000 CFU/lb into their dry matter basis? Is it simply (100%-10%) * 19000 iu/kg for Vitamin A?

Would Calcium be (1.25/90) * 100?

  • Can you include the moisture content of the food in question?
    – Zaralynda
    Dec 11, 2014 at 1:39

1 Answer 1


You don't state the moisture content of the food in your question, so I'll use X as a stand-in. When you find the moisture content of the food, just replace that where I have X.

So, first understand that IU is a measurement of biological activity (how much affect a substance has), and kg is a measurement of mass (roughly equivalent to weight on Earth). For materials such as vitamins that are measured in IU, 1 IU of substance A will have a different mass than 1 IU of substance B. IU is not a mass measurement.

When calculating a percentage, the mass of the substance is divided by the mass of the entire food. When mass is divided by mass, the result is a unitless measurement (percent) because the masses cancel out. Because IU is not a mass measurement, the percentage content cannot be calculated. However, we can do the calculation with IU/kg instead of kg/kg.

Dry Matter Vitamin A Content = 19000/(100%-X%)= Result measured in IU/kg.

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