Dry cat food:
Crude protein …..min. 31.0%
Crude fat ……….min. 24.0%
Crude fiber ……..max. 1.0%
Moisture ……….max. 11.0%
Ash ………………max 8.0%
Wet cat food:
Crude protein ……min. 10.00%
Crude fat …………min. 6.00%
Crude fiber ………max. 3.00%
Moisture …………max. 78.0%
Ash ………………max 2.5%
The above are my reference points for comparison.
First, if you want to just calculate the carb content in one can or one bag, without comparing it to another, the formula is this:
100 – %protein – %fat – %moisture – %ash = carbohydrate
This is because protein, fat, moisture, and carbohydrate = the total weight of the food (100)
We want to isolate the carbohydrates, so we subtract the rest from the total (100) to get it.
Ash is what remains after the food is burned, we want to leave it alone. Do not do any calculations with ‘ash’
Taking my above example of dry food analysis, this is it:
100 – 31% – 24% – 11% – 8% = 26 % carbohydrates, by weight. Pretty simple.
We leave fiber alone because it is considered a carb, so we don’t want to subtract it from the total. In fact, I could take fiber out of this post and we wouldn’t miss it.
To do comparisons for wet and dry, you’ll have to refer to my Calculating Guaranteed Analysis Section post to do the math to get both the wet and the dry in a moisture free state.
So now that we compared the moisture free content of dry food and wet food, we can take it a step further and calculate and compare the carbohydrates.
Just plug in the numbers you calculated from the Calculating Guaranteed Analysis Section into the above (bolded) formula.
I’ve already done the math and I get this:
Dry: 100 – 34.8% – 27% – 8% = 30.2% carbs
Wet: 100 – 45.5% – 27.3% – 2.5% = 24.7% carbs
So the dry food has more carbs.
Again, we are going by the guaranteed analysis section the pet food companies post on the label. These are known to not be 100% accurate. We are using these as a rough estimation.