Calculating Carbohydrates – Carb Calculator
Pet food companies are not required to list carbohydrates on their labels… so they don’t!
It is possible, however, to calculate them yourself.
The calculation is in two steps: first you calculate the carbs on a wet matter basis, then you do a final calculation to find the carbs on a dry matter basis.
In order to start TR, your cat MUST be on a 100% wet food diet that contains a maximum of 10% carbs on a dry matter basis: the closer to the 3-5% carbs in a cat’s natural diet, the better
Guaranteed vs. Nutritional Analysis
The figures that you will find on the label of your cat food are reported in either Guaranteed or Nutritional Analysis.
The Guaranteed Analysis is a mix of maximum and minimum percentages ( a minimum % of protein, a maximum % of ash…..).
The Nutritional Analysis on the other hand, is based on an average percentage for each element. It is therefore more accurate than the Guaranteed analysis.
Unfortunately, while Nutritional Analysis is used in Europe, Guaranteed Analysis is the norm everywhere else. For members living in the US, Dr. Lisa Pierson has created a very comprehensive list of foods and the percent carbs based on Nutritional analysis that may be found here: Dr. Pierson Food Chart .
Please note however that Dr. Pierson compiled her information in the summer of 2012 (some updates have been made since). As companies will change their recipes, some of the data may be inaccurate today. It is good to double check the figures by contacting the company and asking them to give you the Nutritional Analysis figures. Dr. Pierson’s chart, though, can help you narrow down your food choices. She is noting at the top of the list when changes have been made.
Calculating the Carbohydrates
In order to illustrate the calculations below, the following values are used:
• Protein: 9,5%
• Fat: 5,0%
• Fibre: 0,5%
• Ash: 2,0%
• Moisture: 82,0%
1. In order to calculate the carbs on a wet matter basis:
• Add up the % values for protein, fat, fibre, ash and moisture
• Subtract the total from 100
• The difference is the percent carbs on a wet matter basis
Using the values in the example above:
• 9.5 + 5.0 + 0.5 + 2.0 + 82 = 99
• 100 – 99 = 1
• Wet matter carbs: 1.0%
2. In order to calculate the % carbs on a dry matter basis:
• Subtract the % Moisture from 100
• Divide the percent carbs on a wet matter basis by that number
• Multiply by 100
Using the values in the example above:
• 100 – 82 = 18
• 1.0 divided by 18 = 0.056
• 0.056 x 100 = 5.6
• Dry matter carbs: 5.6%
This food is therefore a good choice based on its carb content. Please see the sticky in the Food section of the Knowledge Centre for other important factors, such as ingredients to take into account when choosing the best food for your cat.
While the calculation may seem a little complicated at first, it is easy to do once you have tried it a few times.
Carb Calculator
A “Carb Calculator” that does the calculation for you may be found in the following link. Please click on the words “Carb Calculator” and not on the little icon next to it, which will just show what it is, but will not let you enter any numbers – it is just an image of the calculator (added automatically by the software here).
To use the Calculator open the file, then save it on your computer. You may have a message saying that there is a risk as it is downloaded from internet and/or do you authorize modifications. Click on yes to save the file.
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