How to Convert Calories (kcal) to Grams (g)

Keeping your puppy at a healthy weight is easier by accurately monitoring your pup’s food intake. This article demonstrates how to convert a calories-per-day target to grams-of-kibble-per-day. Knowing this will take the guesswork out of feeding, and ensure those begging puppy eyes don’t lead to an overweight and unhealthy dog.

To motivate this article, recently we switched Tuna from puppy to adult dog food. We needed to update Our Feeding Routine for Behavior and Health. Since our vet offers a text-a-vet service, we texted asking for an updated calorie target and heard back within a few minutes. Our kcal/day target is 1517.

The unit of kcal is identical to a calorie of human food. We will just call it “calories” but note that it is not 1,000 human calories.

We also have our bag of kibble. The bag of kibble lists the nutritional information if you know where to look. On our adult kibble, it was listed like this:

We are looking for “Calorie Content” at the bottom. Let’s parse this: “This diet contains 3489 kilocalories of metabolizable energy (ME) per kilogram or 276 kilocalories ME per cup on an as fed basis (calculated).” Since we are weighing our food (vs using a measuring cup), we only need to further understand the first part.

• “This diet” = this bag of food (yours will vary)
• “3489 kilocalories” = the kcal we are looking for
• “of metabolizable energy (ME)” = ignore
• “per kilogram” = per kilogram
• “ME per cup on an as fed basis (calculated)” = ignore

Now we know the second thing we need: Tuna’s adult kibble has 3489 calories per kilogram.

It turns out physics 101 is useful

We start with what we want: grams per day.

Then take stock of what we know. Our target is 1517 calories per day. Our kibble has 3489 calories per kilogram. We also know that 1,000 grams = 1 kilogram. Remember again that we DO NOT make the same conversation for kcal. So we can change our second fact from 3489 calories per kilogram to 3.489 calories per gram.

Now, let’s set up our unit conversion as:

By writing down these ratios, we can see we can cancel out the calories on the right side of the equation to arrive at our desired grams per day. So with these equations, we can take facts about calories per day and calories per gram, and arrive at grams per day.

Now we only need to enter what we know and plug it into a calculator. We know that we have 1,517 calories per day, and we know we have 3.489 calories per gram (and we know the inverse, or opposite, that we have 1 gram per 3.489 calories.

Finally, 1,517 divided by 3.489 equals 345 grams per day. And that is how much kibble we need to target per day to keep our dog at a healthy weight. And because the calorie target is from our vet, there is no uncertainty. Our job as dog owners is to hit that target, not under and not over. And using this formula when the calorie target changes or when our food changes, will keep us on track as part of Effective Weight Management Strategies.