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Dry Matter Calculator

Created by Kenneth Alambra
Reviewed by Wojciech Sas, PhD and Jack Bowater
Last updated: Jan 18, 2024

This dry matter calculator, or as-fed to dry matter calculator, will help you determine the dry matter content of a particular pet food brand so you can compare it to other pet food brands easily. Use this tool for your as-fed to dry matter calculations when you decide to try other brands but still want to get the same amount of nutrients as your previous product.

In the article below, you will learn the difference between the as-fed basis and the dry matter basis in pet foods and how to calculate the dry matter contents of your pet food, given its moisture content.

As-fed basis vs. dry matter basis

When purchasing food for our pets, we want to choose the best food we can afford so they get the nutrients they need. However, comparing one brand to another requires a better understanding of how to read the guaranteed analysis charts of each pet food product. A guaranteed analysis chart shows the percentage amounts of both macronutrients (protein, fat, fiber, and water) and micronutrients (vitamins and minerals) present in a pet food pack. Learn more about micronutrients by checking out our micronutrient calculator.

A pet food package usually has a guaranteed analysis chart on an "as-fed basis". That means that the nutrient contents are in percentages that take into account the moisture or water content of the pet food.

When comparing two pet foods, we want their moisture contents to be at the same level, ideally at 0%. We call this ideal the dry matter basis of pet food, as it is the percentages of the nutrients after completely drying the food out. Doing so will let us directly compare the number of nutrients present in each of our options. To better understand this, let us consider an example.

Example comparison of pet food. How to calculate dry matter content?

Let's say we want to compare two dog food brands, A and B, with the following as-fed basis nutrient contents:

Image of brand A and brand B dog foods showing their corresponding guaranteed analyses on as-fed basis.

As you can see, Brand A looks like it offers more nutrients than Brand B as brand A only has less water than Brand B. However, the difference in moisture contents means that a direct comparison is not possible, so knowing how to calculate the dry matter content of the dog food is essential. For that, let us perform some dog food dry matter computations. To obtain the dry matter basis percentage of a particular nutrient in a brand of dog food, we can use this equation:

DMB%=AFB%×100%100%M%,\text{DMB}\% = \frac{\text{AFB}\% \times 100\%}{100\% - \text{M}\%},


  • DMB%\text{DMB}\%Dry matter basis percentage of a particular nutrient;
  • AFB%\text{AFB}\%As-fed basis percentage of a nutrient as shown on the guaranteed analysis chart; and
  • M%\text{M}\%Moisture content percentage of the pet food also found on the guaranteed analysis chart.

Using the equation above, let us determine how much protein Brand A really has. By substituting the figures from its guaranteed analysis, we can come up with the following calculation for Brand A's protein dry matter basis percentage (DMB%A\text{DMB}\%_\text{A}):

DMB%A=AFB%×100%100%M%=30%×100%100%2%=30.6122449%30.61%\begin{align*} \text{DMB}\%_\text{A} &= \frac{\text{AFB}\% \times 100\%}{100\% - \text{M}\%}\\[1.0em] &= \frac{30\% \times 100\%}{100\% - 2\%}\\[1.0em] &= 30.6122449\%\\[0.5em] &\approx 30.61\% \end{align*}

Using the same equation, we can also work out the dry matter basis percentage of Brand B's protein, DMB%B\text{DMB}\%_\text{B}, as shown below:

DMB%B=AFB%×100%100%M%=25%×100%100%30%=35.71428571%35.71%\begin{align*} \text{DMB}\%_\text{B} &= \frac{\text{AFB}\% \times 100\%}{100\% - \text{M}\%}\\[1.0em] &= \frac{25\% \times 100\%}{100\% - 30\%}\\[1.0em] &= 35.71428571\%\\[0.5em] &\approx 35.71\% \end{align*}

By following the same dog food dry matter calculation for the other nutrients in each brand, we can produce the guaranteed analysis chart on dry matter basis percentages for both the dog food brands, as shown in the table below:


Brand A

Brand B










After performing the dog food dry matter calculations and viewing the table above, we can now see that although Brand A seemed to contain more nutrients than Brand B at first glance, it turns out that Brand B contains more of each nutrient than Brand A after evaluating their dry matter contents.

Of course, there are still other factors that we should consider when buying food for our pets. Just because one food contains more nutrients than the other doesn't mean it's already the better option. If you have a pet dog at home, you can check our dog calorie calculator or our dog nutrition calculator for much more in-depth guides on choosing the best food for your dog.

How to use our dry matter calculator

Using our tool for as-fed to dry matter calculations is very straightforward. You can check the dry matter basis of any pet food you wish. You can also compare two pet foods, just like we did in our example in the previous section. To compare two pet foods, select the compare 2 products option in the first field of our calculator. Then, enter the as-fed basis percentages of each nutrient for each product in their corresponding sections. You will then see a similar table of results for your convenience.

Suppose you need to compare a pet food with an as-fed guaranteed analysis to another per food with a known dry matter basis guaranteed analysis. In that case, you can also do it with our dog food dry matter calculator. In this case, the product with the dry matter basis guaranteed analysis has its moisture set to 0%.


What is a dry matter basis?

Dry matter basis is the percentages of nutrients in a pet food when its moisture content is 0%. In other words, we get the dry matter basis when we dry out a pet food until there is no water left in it. We do this to easily compare various pet foods, especially when they have different moisture contents.

How to calculate the dry matter basis of dog food?

  1. Subtract the dog food's moisture content percentage from 100%.
  2. Divide a nutrient's as-fed basis percentage by the difference you got from the previous step.
  3. Multiply this quotient by 100% to obtain the dry matter percentage of that nutrient.
  4. Repeat these steps to determine the dry matter percentages of the other nutrients in the dog food.

Is it okay to add water to dry dog food?

Yes, it is perfectly fine to add water to your dog's food, especially when it is dry. Adding water will make the dog food easier to digest, and it can also add flavor to the food when the dog food's flavor mixes with the water. However, don't add too much water as you'll end up with something like a soup.

What's really in pet food?

Pet food usually contains macronutrients such as protein, fat, fiber, water, and micronutrients like vitamins and minerals. Our pets can also get these nutrients from home-prepared foods made from chicken breasts and mixed vegetables. However, it is easier to monitor their nutrient intake with store-bought pet food, which usually has a guaranteed analysis chart that indicates how much of each nutrient is present in a pack.

What is guaranteed analysis on pet food?

The guaranteed analysis is a list of the nutrients in a pack of pet food with their amounts. We can usually see the amounts of the nutrients in a guaranteed analysis expressed on an "as-fed basis." As-fed basis guaranteed analysis considers the percentages of the nutrients in relation to the moisture content of the pet food.

Kenneth Alambra
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